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classical music cataloging systems explained


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At their most basic, there are only two kinds of composer catalogs: 1) thematic, and 2) Informal lists of composers' works.

thematic catalogs

A theme is a subject of discourse, discussion, meditation, or composition. In music, a thematic catalog is a list of compositions in a collection of a single composer, usually arranged in order of opus number or some other specific numbering scheme (i.e., BWV numbers for Johann Sebastian Bach in the catalog by Schmieder, where B stands for Bach; K. numbers for Mozart's music, where K. stands for Köchel, the cataloger of Mozart's music; etc.). Incipits (see thematic Catalog Terminology, below) are often included to positively identify a work.

Perhaps without exception, thematic catalogs are created by catalogers with musicological trainingby scholars. To be worthy of its name, a thematic catalog must be a thorough and comprehensive listing of a composer's works, sometimes including biographical studies or other information. The cataloger's goal is to compile as complete and as error-free an account as possible of a composer's works given what is known publically to musicology at the time of compilation and what is known privately to the cataloger as the outcome of his personal researches.

Creating thematic catalogs is an exacting undertaking demanding scholarship because reliable historical information about a composer or his works may be difficult or impossible to obtain and because the accuracy of the data in catalogs must be beyond reproach wherever circumstances allow. These data must be correct and complete because they are used as a basis for the publication of critical editions of musical scores, for historical studies of composers' lives and works, and for analyzing the music itself so as to make visible the composer's precise musical intentions.

  • Literally hundreds of thematic catalogs have been created over the centuries by literally hundreds of catalogers, catalogs that list the works of literally hundreds of composers. To quickly get an idea of some of the most prominent ones, see a list of some of their names at the MUSIClasical.com web site: click here.


thematic Catalogs online?

The Muse Of Music knows of no thematic catalog that is available online at this time; all extant thematic catalogs come in the form of printed documents. However, some online catalogs approach the quality and comprehensiveness expected of a thematic catalog, especially those published at university web sites.

If you know of exceptions, please contact The Muse Of Music.

informal lists of composers works

Informal lists of composers' works are lists of that do not conform to the rigid scholarly requirements of a thematic catalog; hence they are here-dubbed informal.

Informal catalogs share a common primary objective with thematic catalogs, namely to list the works of a single composer; but the lists of works in most informal catalogs may not be complete; the citations may not be as accurate; the listed works may not be elaborated with as much supplementary information or with the same kinds of information; and the lists may be out-of-date or defunct.

  • To quickly get an idea of what informal lists of composers works are like, visit the page titled Works Lists at the ClassicalNetTM web site. It contains a list of the names of composers, each conjoined with the name of his cataloger. Once you arrive at this page, click a few of the composer's names. Each click will take you to a page at the ClassicalNetTM web site or at another web site that contains a catalog for that composer that was created by the named cataloger: click here.

Most if not all of the catalogs named on this list of catalogs are informal. Notice that many of them no longer exist; they are defunct. Some of them list two or more catalogs for the same composer. (The Muse suggests that you check to see whether the catalogs agree with one another in cases where more than one catalog is listed for the same composer.)

Many informal catalogs are modeled after thematic catalogs in one key respect: they incorporate a numbering system borrowed from a popular thematic catalog. For example, an informal catalog which lists Schubert's works is likely to identify each listed work by the same number that is employed by Deutsch in the Deustch thematic catalog. In such a catalog, Schubert's Quintet, D.956 might be identified by the number D.956, the same number and catalog designator as cited by Deutsch. It might (or might not) also contain the popular name of a work. For example, it might or might not list Schubert's Symphony No. 8 as the Symphony No. 8 in B minor, D.795, known as The Unfinished Symphony.

Informal lists come in many shapes and sizes: they come as web sites; they come as books; they come in books, as sections, chapters, or appendices of a larger work about a composer, musical period, musical style, or movement; and they come as notes, footnotes, or appendices. they appear in almost any kind of printed form or medium.

Why informal lists? Most informal lists are compiled by classical music lovers, armchair musicologists, authors, classical music loyalists, fans of a specific composer, organizations that seek to promote a particular composer's music for various reasons, classical music popularizers, backers of specific classical composers, and by composers who seek to promulgate and promote their own compositions; even businessmen, national groups, and others get in the act, all with primary agendas or vested interests other than scholarship alone.

Many of the lists of composer's works found on the Internet are of this variety. For example, one can find informal lists on the Internet that are compiled by a French cultrual organization to promote French culture, by a similar Spanish cultural organization, and by a promoter of Soviet classical music (yes, Soviet, not Russian). A number of web sites offer informal lists of composers' works as a courtesy to music lovers and to attract visitors who are likely to buy the recordings they sell in the Virtual Mall, a not-so-hidden agenda.

thematic catalogs and informal lists compared

Compared with thematic catalogs, informal lists have distinct advantages and disadvantages. Despite a typical lack of scholarly authority or comprehensiveness, informal lists tend to be handy and easy for the casual observer to use and understand. If on the Internet, they are likely to be easier and lest costly to access, and in many cases their listings can be searched with a browser.

Informal catalogs on the Internet are more likely to offer a computer-generated index of one sort or another, and they might even offer multiple indexes for a single composer's works or multiple lists of for multiple composers, each list organized in a different way. In a hypothetical example, a J. S. Bach catalog might be sorted by BWV number, date, opus number, and the name of the piece. A catalog of Vivaldi's works might be arranged by the names of multiple Vivaldi catalogers (e.g., Ryom number, Fanna number, Pincherle number, and Ricordi number), opus number, instrumentation, and type of music (e.g., opera, instrumental).

Most thematic catalogs contain only a single listing, while many informal catalogs contain multiple listings. These facts are easy to reconcile with one another when one considers that most thematic catalogs were created before the advent of computers, when printing was the only practical publication medium; but most informal catalogs, which are relatively recent developments, were created after the advent of computers and are published at web sites, where computers are involved in their preparation.


thematic catalogs vs. Informal catalogs

Except as otherwise indicated, much of what can be said for thematic catalogs applies to informal lists of composers works to one degree or another. Please keep this fact in mind as you read the sections that follow on this page.

catalog Contents

There is no standard way to organize a catalog of musical works. As a consequence, no two catalogs are exactly alike; each is unique.

Normally, a thematic catalog will contain, at a minimum:

  • Name of a work. For example, Dvorak Symphony #3.
  • Poplar name of a work. (Dvorak's String Quartet No. 12 is nicknamed The American.)
  • Musical description—For example, musical form (e.g., sonata, symphony, opera); number and kind of instruments or voices scored (e.g., two pianos, orchestra, orchestra and chorus); key; movement tempo; etc.
  • Associated information that serves to identify the workFor example, an incipit, a description of when or where the work was composed, names of co-composers, names of librettists, etc.
  • Opus numberA number that normally conveys the order of publication (see Thematic Catalog Terminology, below).
  • Publication date.
  • Work number—An ordinal number which indicates the sequence in which the composer created a specific work in comparison with other works of a similar nature. For example, piano concerto No. 2, etude No. 4. (see Thematic Catalog Terminology, below)
  • Catalog number—the ordinal number assigned by a cataloger that designates the order in which a work was created by a composer as compared with all his other works.

how thematic catalogs work

By custom, a single cataloger (or perhaps, two or more catalogers together) compiles as complete a list as possible of the works of a single composer. By tradition and for obvious reasons, such a catalog usually takes the name of the composer, not the person who compiles the catalog.

How opus numbers are assigned to composers' works

Each work in a typical catalog bears a number called an opus number (work number), a unique mark that identifies each specific work created by a single composer or his collaborators. The opus number is usually assigned by the publisher at the time a work is published; if not so assigned, it's assigned by the person or group who creates (compiles) a catalog of a composer's works, a person referred to as a cataloger or compiler.

The publisher or cataloger assigns this opus number to each work to identify it for posterity. The number is a sequential number that is usually assigned in the chronological order of publication, not necessarily in the order of composition. In this connection, the word opus is used to denote a particular musical composition; and the catalog number, publication number, and opus number are usually, but not always, the same, a circumstance which can potentially create confusion.

Why not always the same?

Most often, composers and collaborators choose to create and publish one new piece of music at a time, as soon as practicable after a work is finished; they want to meet a deadline, collect a fee, or obtain recognition. In cases like these, the opus number is unique and no confusion arises because the printed document that contains the new score contains a single piece of music.

In cases like these, typically a publisher assigns a single, unique opus number to the composition at the time of publication. Notice that the unique opus number assigned to a work is synonymous with the name of the document that contains the score because the score's opus number is printed on the face of the document; the score and the printed document are universally identified with each other because they carry the same number. No confusion arises because the document title and the opus number are identical.

But confusion potentially does arise when composers and collaborators choose to publish more than one work in the same document. This can happen for a multitude of reasons: when a composer chooses to combine the publication of completely separate works that he's composed at different times; when a composer publishes separate but related pieces such as several pieces belonging to the same suite or several overtures for the same opera or play; when there are several musical accompaniments for acts in the same play; or for a number of other reasons.

In situations like these, a publisher has two choices: either he assigns a separate and unique opus number to each work published in a document, in which case the document cover must display all of the different opus numbers if it is to represent them; or, he assigns the same opus number to all the works in the document, in which case the document cover must display only a single opus number; and then each of the works is not uniquely represented on the cover.

In circumstances like these, publishers usually take the middle ground. They assign one opus number to the document and another, unique opus subnumber or sequence number to each of the works contained within. The opus number on the document cover uniquely identifies the group of works and the work subnumber distinguishes one work from another.

This policy enables a single document to use one opus number to represent all the works published by a single composer at a given time, thus providing unequivocal cover recognition for the group of works the document contains and rendering the document synonymous with all the works therein.

It's important to realize that, in cases like these—when multiple works are published in the same document at the same time—the opus number, which by definition represents a single musical composition, actually represents a group of related compositions. The group opus number is considered to be synonymous with an entire single musical composition, not the individual pieces.

How opus numbers are assigned to specific works—listing numbers

Each entry in a catalog provides information about each specific work, information which uniquely identifies and describes the work. Some of the items of information that typically are listed:

  • formal name of work
  • popular name of work (if any)
  • opus number
  • musical key
  • date of publication
  • publisher
  • co-composers (if any)
  • author of libretto (if an opera or choral work)
  • dedication (if any)
  • type of ensemble for which a work is written (if written for group or orchestra)
  • solo instrument(s) for which written (if the work features a solo instrument), and more.

A code is normally added to or associated with the number assigned to each work cited in the catalog. This code identifies the catalog in which the composer's works are numbered.

So, for example, the selection you hear when you open The Muse Of Music's home page is cataloged as Schubert's Quintet, D.956, where the D. is an abbreviation of the word Deutsch. Deutsch is the name that denotes the catalog; it is also an abbreviation of the last name of the person who compiled the catalog. The number 956 refers to the fact that Schubert's quintet is the 956th of Schubert's works that have been created, as cited in Deutsch's catalog.

Most, but not all, catalog names take their names eponymously from the name or names of the catalogers; and the abbreviations of these catalog names are taken from the initials of the catalogers. Thus the initial D. is an abbreviation of both the catalog name and the cataloger's name, Deutsch.

The composite of the catalog identifier code and the catalog number is sometimes referred to as the listing number because it is the number by which the composer's work is listed in the named catalog.

Why note a catalog's listing number? Once you know a work's catalog and sequence number, you are in a position to look up the information recorded by the cataloger in his catalog.

Why knowing a catalog's listing number is useful

The information in these catalogs is often quoted when a piece is broadcast on the radio or played in a concert hall. Catalog number is rarely omitted from the typical printed musical program distributed at a concert performance. It is common practice to cite the cataloger's name when announcing the opus number or other cataloged facts about a musical work. Thus, Scarlatti's Opus 21 might be referred to as Scarlatti Opus 21 in the Kirkpatrick catalog, or with some similar designation in another catalog, to clear up any questions about the source of the information.

Professional musicians have come to regard music catalogs as necessary. Most are authoritative, definitive compilations; scholars rely on them as authoritative sources for their research. they are in widespread use today as standard musical references and they rely on them for scholarly research.

These catalogs are so well established in the minds of musicians and listening audiences, it is common practice to abbreviate the cataloger's name using a code derived from the cataloger's initials, although this is not always the case. Thus, a designation such as  Mozart's Opus 351 in the Kochel catalog might well take a form such as, Mozart's K 351 (with K standing for the compiler Kochel's catalog and 351 standing for the publication sequence number assigned by Kochel).

thematic catalog terminology

As you read thematic catalogs or as you read about catalogs you are likely to encounter a few specialized terms use by musicologists and musicians. Here are a few such terms, some of which are abbreviations and some of which are not, with definitions and supplementary explanations that may help you decipher what they mean.

  • Thematic

Perhaps the most fundamental term that comes up in connection with the subject of music catalogs is the word thematic. Most, but not all, music catalogs are thematic catalogs.

Music catalogs that are thematic catalogs are called thematic because they aim to include the musical notation for the principle themes or tunes of each work they list. These notes are meant to serve as an aid in identifying the works. They do this by means of an incipit. See a definition and an explanation for the term incipit, below.

  • Work number

A work number is an ordinal number that indicates the order in which a composer has created a specific work in comparison with his other works of the same kind.

Work numbers are assigned to a composer's works in the sequential order in which the composer has written works of a similar type. For example, usually a composer will write his Symphony No. 4 before he writes his symphony No. 5 or his piano concerto No. 2 before he writes his piano concertos No. 3, No. 4, or No. 5.

Work numbers are normally assigned to a composer's works by catalogers rather than by composers. theyare almost always present in a classical composer catalog.

  • Thematic catalog number (also sometimes referred to as work number)

A thematic catalog number is an ordinal number assigned to a specific work in a catalog which indicates the order in which a composer has created the work in comparison with all his other works, regardless of their type. The thematic catalog number for a specific work is unique; it differentiates each work written by a composer from every other work.

Thematic catalog numbers are normally assigned to a composer's works by catalogers rather than by composers. theyare always present in a classical composer catalog.

Thematic catalog numbers are usually expressed in the form of a coding system that is especially developed by the cataloger for the catalog he is creating. (In some cases, a cataloger will borrow a coding system devised by another cataloger.)

The coding system developed by cataloger Martin Ruhnke and published in his thematic catalog for the works of Telemann titled Georg Philipp Telemann: thematisch-systematisches Verzeichnis seiner Werke provides us with an example of a cataloger-developed thematic cataloging system. Work numbers in Ruhnke's catalog for Telemann are encoded in a format such as TWV 41:a15. In this example, TWV is shorthand for the name of the catalog and 41:a15 is the specific, unique work number Ruhnke has assigned to one of Telemann's works in this catalog. This number assignment sets this work apart from every other work Telemann has ever written.

Ruhnke has not gone to the trouble of developing this particular numbering system when a simpler one might do equally well; he has not been capricious. The historic circumstances under which different composers create music can be unique; the nature of their output can be unique. Each composer can pose intellectual and scholarly cataloging problems that are best solved by a numbering scheme that's tailor-made to suit these factors.

NOTE: 1) A thematic catalog is a catalog of all of a single composer's works, usually but not always organized by type of music, and arranged in in chronological order. 2) When new information comes to light, some catalogs, especially those for composers in whom interest runs high, undergo revisions and are republished in new editions. Typically, different editions of the same catalog are noted by decimals, as in KV, K.2, K.3,..., K.6. In this example, KV stands for Kochel's original catalog, K.1 for its second edition, etc. 3) A catalog of his own works created by a composer will often bear the composer's initials, as in MozV, which stands for Mozart's own directory of his works.


work numbers and thematic catalog numbers

The term work number has two senses: 1) the thematic catalog number, and 2) the order of a work compared to other works of the same type.

A work listed in a thematic catalog will always have a work number assigned to it (sense #1). Sometimes the description of a work will also contain a work number that indicates the order of its composition compared with other works of the same type (sense #2).

Don't confuse the two numbers.

  • Opus; opus number; op.; or Op

    An opus number is a unique number assigned to a composer's work or group of works, usually in the chronological order of publication. (Opus is Latin for the word work; and the plural of opus is opera.)

    By definition, an opus number represents the order in which a work is published, not the order in which it is composed. Sometimes an opus number is assigned to a work by its composer, but more often it is assigned by a publisher. Opus numbers are almost always present in a classical composer catalog.

  • WoO

WoO is an abbreviation for Werk ohne Opuszahl (German) or Work without opus number. This term appears in classical music writings generally, but especially in classical music catalogs. The kinds of works marked WoO in catalogs are typically unpublished works or groups of works that have not been assigned an opus number.

  • Incipit

An incipit is a kind of musical fingerprint that helps to disambiguate a piece of music. It consists of a small group of the first few notes, measures, or lyrics with which a piece of music begins, notes that are are unique to the piece.

Incipits are often given in thematic catalogs in order to positively identify a piece of music. In the case of works with multiple movements (such as symphonies, sonatas, or suites), an incipit may be supplied for each movement or piece a work contains.

  • Deest, Desunt

Deest is a compound Latin word meaning absent or not present; desunt is the plural of deest. Deest is derived from two Latin words (de and est) that have been merged into one (deest), where est means is and de denotes negation.

The terms deest and desunt are used in musicology generally, but they occur especially in connection with catalogs of composers' works. If you see deest in the write-up of a work listed in a catalog, you know that the work does not appear in another catalog that will be cited in the write-up. It's not present in the cited catalog.

For example, the comment K. deest occurring in the write-up of a work listed in a catalog indicates that the work does not appear in the Kochel catalog of Mozart's works, even though it appears on the page of the catalog you're looking at. (The Kochel catalog is abbreviated K.). Another example: BWV deest occurring after a work listed on a page in a catalog you're looking at would indicate that the work is not present in the Schmieder catalog of Bach's works. (The Schmieder catalog is abbreviated BWV.)

  • Verzeichness

A verzeichnis is a German word meaning catalog or directory, as in the term Bach-Werke-Verzeichnis, or Bach Works Catalog. In the German language, any kind of catalog is a verzeichnis; the word is not restricted to music.

The term verzeichnis is often seen in connection with composer catalogs compiled in the German language. Historically, that's because many composers were German, with the result that many composer catalogers were German.

Since many recent and contemporary music scholars and musicians of all nationalities work with these German catalogs, verzeichnis is a word familiar to them, regardless of their native language; the word has passed into the general vocabulary of music.

Systems for cataloging classical music—a definition

As explained above, a classical composer catalog may optionally contain these kinds of codes and numbers:

  • Opus numbers, which indicates the accepted publication sequence for a specific work.
  • Work numbers (sense #1), which indicate the accepted sequence in which a specific work was created in relation to other works of the same kind.

Also, a classical composer catalog will always contain thematic catalog numbers (or work numbers, sense #2). Each of these numbers uniquely identifies a specific work and indicates the sequence in which that specific work was created in the context of the complete body of a single composer's works. In addition, any particular thematic catalog number unifies and associates opus number, work number, and all other pertinent information about a specific piece, including qualifiers which explain and resolve problems with opus numbers, work numbers, and other discrepancies, if any.

A system for cataloging classical music is a particular combination of these codes and numbers.

The encoding systems and numbers for listing a composer's works that appear in a thematic catalog amount to a system for cataloging the classical music of a single composer. A given combination of these numbers and numbering schemes constitute a specific system for cataloging classical music as devised by a particular cataloger for a particular composer.

The two specific numbering schemes cited above (i.e., Schmieder's BWV numbers for Johann Sebastian Bach, where B stands for Bach; K. numbers for Mozart's music, where K. stands for Köchel, the cataloger of Mozart's music) are examples of numbering systems for cataloging classical music.

In the example drawn from Mozart's piano concertos in the discussion of what can go awry with opus numbers, above, cataloger Kochel sets right the publication order and work number order for Mozart's piano concertos by assigning his K. number to Mozart's works.

Because they tend to be trustworthy, a numbering system devised by a cataloger, such as Schmieder's numbering system or Kochel's numbering system, occasionally comes into common usage in the world of music.

Problems that can occur with thematic catalogs

You may run into problems when you work with catalogs; watch out for them.

  • Here a few of the most important problems and what you can do about them: click here.
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