# Song #, Op. #, & K. #: What do they all Indicate?



## Captainnumber36 (Jan 19, 2017)

I just realized that while listening to my Beethoven Cello Sonata disc, there are multiple No. 1s with different opus numbers.

What exactly does each number represent? (very noob question, I thought I had this down, I guess not!)


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## EdwardBast (Nov 25, 2013)

An opus number is used for a work or set of works appearing under the same cover as a single publication. So, for example, Beethoven's Quartets Op. 18, nos 1-6, are a set of six quartets published together. The opus number indicates that this was Beethoven's 18th publication. Up until that time it was common to publish works in sets of 6 or 12, although sets of three became common when individual works started to get longer (e.g., Beethoven's Sonatas Op. 31 or String Quartets Op. 59.) For example, Vivaldi's L'estro armonico, Op. 3, was a publication comprising 12 concertos. They would be designated as Op. 3 no. 1, Op. 3 no. 2 and so on. 

So, taking another example from Beethoven, if one published two sets of sonatas each comprising three works, one might have Op. 10 no. 2 and Op. 31 no. 2. The numbers are there to distinguish the works within a set. Adding another complication, Op. 10 #2 is often referred to as Beethoven's Sonata no. 6 and the Sonata Op. 31 #2 is his Sonata no. 17. In this case the numbers indicate the order position in Beethoven's overall output, regardless of how they were grouped when published.


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## jegreenwood (Dec 25, 2015)

And just to complete the response, K. Is for Kochel number and is specific to Mozart. That is a listing by Ludwig van Kochel of Mozart's pieces in his best assessment of chronological order. None (a few?) of Mozart's works were issued with Op. Numbers.

Bach's works are assigned BWV numbers, but those are generally by type: no attempt was made to number them chronogically.


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## MarkW (Feb 16, 2015)

And Schubert's works have a "D" number, for Deutsche who first catalogued his works, and tried to do it chronologically (as best you can do for 900+ works, many of which lay hidden in drawers for years. )


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