Telemann's works are numbered first according to genre, then, where applicable, by key (with minor keys in lowercase and major keys in uppercase), and finally (if possible) chronologically or else at random. For example, TWV 51:G9 is the famous viola concerto in G major, where the category number 51 denotes concerti for one solo instrument and orchestra.

It seems like such a neat and rational system; which is why I wonder why it isn't adopted more universally. Are there any musicological reasons against its wider application? In my mind, certain prolific composers, such as Vivaldi, would benefit tremendously from a TWV-like catalogue.

  • I can't confirm this in respect to CD recordings, where established labels publish that information routinely. I observe, that for the music collector this information is more important than for the player (where other criteria like degree of difficulty overshadow this) , so sheet music editions frequently save the effort to research and add those as well. For Vivaldi the Ryom-Number (abbreviated RV) is also well-established, as BWV for J. S. Bach and Deutsch (abbreviated D) for Schubert, and Köchel for Mozart.
    – guidot
    Commented May 8, 2020 at 19:14

2 Answers 2


A cursory look at the Wikipedia article for opus number gives me the impression that publishers generally trusted the opus numbers composers assigned to their own works, to the point where they did not further renumber by genre or piece type first. Notably, opus numbers are generally in ascending publication order, revealing insightful information a numbering system by genre/piece type first masks. For musicology purposes, I love investigating the development of a composer's style, and that is made easier if I know the order a composer finished his/her own pieces - which opus numbering generally corresponds to. (Even inconsistencies in opus numbering can reveal a composer's hesitancy to get certain works published or a love of categorizing his/her own works.)


Such numbering systems exist for many composers. Different scholars have created these catalogs, and so there are different organizational systems adopted.

In my mind, certain prolific composers, such as Vivaldi, would benefit tremendously from a TWV-like catalogue.

I'm not certain from the wording of your question -- are you aware of things like the Ryom Verzeichnis (RV) numbering for Vivaldi's works? While it doesn't separate the numbering for key and subnumber as the TWV does, it does generally group works the same way, i.e., by genre, by instrument, and then by key.

Such scholarly catalogs and numbering systems exist for most major classical composers. (Vivaldi's works actually have at least three such scholarly catalogs, each with their own numbers.)

However, you are correct that not all such scholarly editions or catalogs of works group them in the same way. The standard numbering for Bach's works (BWV) is also grouped by genre, but, for example, the standard catalog for Mozart (Köchel Verzeichnis, or KV) attempts to number works chronologically. A major problem with the latter approach is that many works cannot be precisely dated, and later modified estimates for dating have led to numerous revisions of the KV numbers, often with appended letters to the numbers for works that have to be inserted in different places. Another problem shared by consecutive numbering systems from KV to BWV to RV is what to do with newly discovered works. Are they simply added at the end, thereby divorced in numbering from other works in their genre because of historical accident? Are they inserted (e.g., with appended letters or something to indicate their placement)? Is the entire catalog renumbered?

I agree that the TWV system avoids many of these problems, but we should remember that these works catalogs have developed over time as scholars have realized the various problems with previous numbering systems and tried to avoid the errors of those before them. The Köchel Verzeichnis for Mozart was first published in the 1860s and was one of the earlier attempts to number a composer's complete works. For Mozart in particular, there was also a particular interest in chronology (as he was known as a child prodigy, so it made sense to try to separate out his early works by numbering).

Nowadays, it's easy to look back and see the folly in trying to organize a catalog in such a fashion, but we stick with the KV numbers because they are already known and traditional. It's easier to publish a revised catalog with a few revised numbers rather than trying to get every edition of music out there to shift to completely different numbers for Mozart's works.

Consecutive numbering for all works (as in the BWV) became standard for a few generations, but it too suffers from problems and the need for renumbering.

Telemann was in some ways the benefactor of later scholarly interest. Although he was incredibly famous and influential in the 18th century (as well as a prolific composer), he fell by the wayside a bit compared to early scholarly interest in composers like Bach and Handel. The TWV numbering was only created and finalized in the 1980s and 1990s, so I think it benefited from hindsight in its numbering design. Some complete editions of works by other composers have adopted similar numbering systems in recent decades.

Even for scholarly editions that don't adopt a formal numbering system, a similar system to the TWV is often in place, where volumes are often numbered within genre first, and individual works are found grouped within those bands of volumes. These multitiered numbering systems are frequently used by scholars, but don't tend to appear much for referencing works outside of scholarly articles.

Unfortunately, as I said, the problem is that numbers like KV or BWV are so well-known that it's very difficult to propose a completely new numbering and supplant those numbers now, despite their flaws.

And of course for later composers (like Beethoven), a much higher percentage of their works were actually published during their lifetimes, so opus numbers become more important and relevant for convenient reference.

  • Your criticism of Köchel's catalogue would apply to every system of assigning opus numbers. If organising by genre is so good, then why bother with catalogue numbers at all? unless a work has a name (e.g. a song or cantata) why not identify it by genre and number, e.g. Cello Suite 1 in G, Symphony 41 in C etc.?
    – Rosie F
    Commented May 10, 2020 at 5:56
  • 1
    @RosieF: No, my criticism of Köchel's catalog has to do with assigning a series of consecutive numbers based on a sequence that will be subject to revision (e.g., uncertain dates of composition, missing or previously unknown works). Opus numbers are certainly not the same, as they are rarely altered post-publication. And your system is as good as any. I'm not arguing for any particular system, just trying to answer OP's question. My "criticisms" (such as they are) are not about the priorities in organization, but rather methodologies for numbering that necessitate renumbering or confusion.
    – Athanasius
    Commented May 10, 2020 at 6:18
  • @Athanasius: Thank you for your excellent answer. Yes, I'm aware that Ryom's catalogue also catagorizes by genre and key. My problem is that it does so in a rather opaque way; you really have to know about it beforehand to get any benefit from it. (I should have made that clearer.) Commented May 10, 2020 at 13:22

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