Piece Labels

If you’ve ever wondered what the labels at the top of pieces mean – things like Op.1 or K.500 – this guide should help you understand. It doesn’t explain the exact meaning of every possible label you’ll see, but it will give you enough understanding to recognise what they are, why they’re there, and know where to find more information if you want it. The main point for each paragraph is in bold at the top if you only want the basics, while the full text gives more detail and examples.

Pieces need labels
Pieces of music need some form of organisation for us to be able to find them, let alone talk about them. If I want to find the sheet music for a sonata in G major by Scarlatti, I need to know which of the 70 I’m talking about (that’s not an exageration by the way, Scarlatti genuinely wrote 70 sonatas in the key of G major). Over the years, various scholars and publishers have done their best to put labels on pieces to make life easier. After several hundred years of different helpful catalogues and labels, the resulting pile of numbers and letters after pieces of music might seem like a confusing mess at first – and in many ways it is – but it’s not so bad once you understand what’s going on.

Opus numbers tell us how many pieces a composer has published so far (in theory)
The most common numbering system for musical works is an “Opus” number. In theory, these numbers are given to pieces when they’re published – the first work a composer publishes will be Op.1, and the list will go on chronologically from there. We can assume that a composer’s Op.5 was written before their Op.40 for example. If the composition is a set of pieces then you’ll often see the a ‘number’ on specific works as well – this tells us where in the original collection we can find the piece. For example, the second piece from Schumann’s Album for the Young Op.68 is called ‘Soldier’s March’: If you see that piece in an anthology or exam book, it will be labelled as Op.68 No.2. This is straightforward, easy to understand, and very helpful.

Relying on opus numbers has a lot of problems
In practise, opus numbers are often incomplete, innacurate, or only give part of the story. It’s probably easiest to list the reasons as bullet points:

  • Not every composer used opus numbers to order their works, especially before the 18th Century
  • Composers sometimes published old pieces when they became succesful, meaning that the order of publication doesn’t necessarily match the order of composition
  • Not everything a composer writes is published, so there are plenty of pieces without an opus number, even a composer generally used them
  • Publishers didn’t always keep great records of how much a composer had written (especially since previous compositions might have been published by other companies in other countries). Occasionally, pieces were labelled under an opus number that had already been used before (so we might end up with two different pieces both labelled as Op.6)
  • Publishers would occasionally deliberately use a higher opus number to make someone sound more established, because works by established composers tended to sell better

Scholars have produced catalogues of individual composers’ work
Understandably, some musicians want a more complete picture of what composers wrote and in what order. A whole range of scholars have spent thousands of hours producing detailed ‘catalogues’ of a particular composer’s works over the years. While these catalogues share a lot of similarities, they were generally the work of individual scholars, so there are plenty of differences between them. This means the works of different composers often have their own unique labelling system, usually named after the person who put the catalogue together.

Some examples of individual catalogues
Anthony von Hoboken put together the most widely used catalogue of Haydn’s work, to take one example, so Haydn pieces have a Hob. Number. Mozart works have a K. number because of the catalogue by Ludwig Ritter von Kochel, while all 555 of Scarlatti’s sonatas also have a completely seperate set of K. numbers because of the catalogue by Ralph Kirkpatrick. I’m mentioning those examples because it’s important to remember that the catalogues are unique to a composer, even if the letter used happens to be the same.

Catalogues are organised in different ways
These catalogues are organised in different ways, depending on the scholar. Kochel’s catalogue was chronological, so a label of K.1 was given to what he thought was Mozart’s earliest work (some short piano pieces), right through to Mozart’s last composition (the Requiem mass) which was given the highest number, K. 626. This way of cataloguing pieces is straightforward, but can be frustrating if you just want to find a particular type of piece. The other approach was to organise by genre and then chronologically. Hoboken did this with the Haydn catalogue, so his pieces are labelled with the category and then the piece number. For example, Haydn’s string quartets were grouped together as the 3rd category in the catalogue while the piano sonatas were the 16th – the 8th string quartet is Hob. III:8, while the 8th piano sonata is Hob. XVI:8. If that seems fussy, it might be worth bearing in mind that the Haydn wrote so much music that Hoboken’s catalogue was over 2000 pages long. Splitting it into manageable sections wasn’t such a bad idea!

Catalogues can change over time
Sadly, things get a bit more complicated again. Catalogues of works can only be based on the information available at the time. New works can be discovered in unexpected manuscripts, and scholars find out that pieces we thought were written by a particular composer were actually written by someone else. New knowledge about a composer’s life can also reveal that pieces were written earlier or later than originally thought. Armed with that sort of new knowledge, catalogues can be revised or completely new catalogues can be made. It makes sense to do this, but unfortunately for us, it means that pieces can end up with multiple labels.

If a piece ends up with multiple labels, you might see them all
Generally when a piece has multiple labels, publishers try to use all of them on new editions of the music. After all, if a piece was labelled in a particular way for over 100 years, that label is going to be in people’s heads, as well as in books and on recordings, so it makes sense to include it alongside any newer labels. It’s a bit messy, but gives everyone the best chance of finding and identifying the piece, while keeping up with the latest information we have. I’ll finish with a couple of examples. Going back to Mozart, the Kochel catalogue is now in it’s 6th edition, and the numbering of pieces has shifted. One of my favourite sonatas (the one in Am), used to be K.330 but is now K.300h – In more recent editions, you might see the piece labelled as K.330/300h. As for Haydn, the piano sonatas were renumbered about 50 years ago by Christa Landon. Suddenly, the sonata which was number 8 in the Hoboken catalogue was called number 1 in the new system, so you’re likely to see labels like ‘Sonata No.1 in G, Hob.XVI/8”. The labels you see on different editions might be a little different, especially if one edition is older than another, so you might want to use all available labels when you’re searching for a piece!

Final Thoughts – How to use labels
If all that seems a little overwhelming, remember that labels on pieces are just tools to help us identify them. If you’re not sure what a particular label stands for, feel free to look it up if you’re curious – something like “what are D numbers in Schubert” should give you the information you need, to take one example (to save you time, the Schubert catalogue was compiled by Otto Erich Deutsch and organised chronologically). There’s no need to try and learn or memorise the different catalogues, just look them up as you come across them if you’re interested – over time, you’re likely to get to know the labels for the composers you enjoy most anyway. If you’re feeling adventurous, you can even explore a composer’s catalogue of works to find new pieces to play or listen to 🙂