I often hear references to, e.g., "Bach's Fugue in G Minor," sometimes with a number (something like "Bach's Fugue in G Minor #13"). Why is the key of the piece so important that it becomes part of the piece's name? Is the absolute pitch of the notes so central that it would be a different piece if transposed up a whole step--perhaps because it's easier to play some tones on certain instruments?

Or were there just a ton of pieces out there that needed names, and whatever key the composer had chosen was as good a way as any to differentiate them?

Related: Why classical music compositions are named with key/scale/note names?

  • Good question. My guess is that, for people who know the piece by ear, the key is often the one thing they need to know in order to play along. Not sure if this is relevant though.
    – Lee White
    Jul 17 '14 at 22:27
  • This was before a maturely-developed discipline of marketing for artists would mandate that every bit of music has a uniquely identifiable and catchy name. ;)
    – Grey
    Jul 19 '14 at 2:57

"Fugue" is just a form and style of composition of which Bach alone wrote hundreds. Same thing for "Sonata", "String Quartet", "Symphony", etc. it's not that the particular key is of central importance or that transposition would necessarily change the piece entirely, it's just a convenient way to distinguish between various iterations of the same form. They also used opus number (and sometimes numbering internal to the opus number) to make the distinction even clearer.

For the most part, the idea of uniquely titled compositions—at least commonly—is a relatively recent phenomenon.

  • I disagree about the importance of the key. In my comment to the first answer I tried to spell that out. The key was basically all important back then. Jul 17 '14 at 18:56
  • 3
    I'm certainly not saying that key is unimportant, just that that's not why it's used in the title of pieces. As you point out in your other comment, key was automatic, a fundamental part of the background structure of any piece. Jul 17 '14 at 19:01
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    At the same time, pieces were often transposed to other keys without that being seen as destroying the identity of the work. In Bach's day, there wasn't even a single idea of a reference pitch, and pieces would sound in a different key on different organs without anyone considering that to be destructive. Jul 17 '14 at 19:03
  • This question got a number of good answers and it was not clear which one to accept. I would highlight PatMuchmore's comment that pieces were often transposed, and that there wasn't a single reference pitch, at the time these pieces were being composed. And I'd add @MunchWilly's note that "Different keys had different tunings and hence sounded different before the widespread use of equal temperament."
    – kuzzooroo
    Jul 19 '14 at 22:55

These are all good answers, but I'd just add a historical note. Composers before the time of, say Beethoven, composers like Bach and Mozart, often did not publish all or even most of their musical works, either because no one wanted them, or because they wanted to keep the pieces for their own use. The vast majority of Bach's music was not published in his lifetime, so there was little need to "name" the compositions. Often the names we use (Brandenburg concerto; Jupiter Symphony) were added later, as nicknames.

Neither Bach nor Mozart left any definitive catalog of works (Mozart wrote up a list from memory late in life, as I recall, but he got things wrong). It was left to musicians and musicologists to find all the manuscripts, try to figure out what order they came in, give them some numbering system, and then publish them in large collected works editions. Most of this editorial work did not even start until well after the composers were gone, at the end of the 19th century.

(This is where the letters and numbers after many 18th-ct. works come from: they are catalog numbers, like Mozart's K numbers, K being Koechel, the editor of the first Mozart edition, or J.S. Bach's BWV numbers [standing for Bach Werk Verzeichnis, or Bach Work Catalog in German]. Even Beethoven left a bunch of works unpublished at his death; they are in his collected edition with W.o.O numbers, standing for "Werke ohne Opuszahl" ["works without opus number"].)

So, in his lifetime, Bach, like most composers, never needed to give distinctive names to most of his works, because most of them were never intended to be used by anyone but him. The full numbering of, say, Haydn symphonies was a real mess, because for most of his life, Haydn just wrote symphony after symphony for his patron(s), who owned them as absolutely as they owned paintings or sculptures they commissioned. When he got famous, some of "his" symphonies became well-known and published, but even those were likely to have been in short numbered sets of, say, six or twelve, like the so-called Paris (82-87) and London (92-104) symphonies. (I used to play four-hand arrangements of Haydn's late symphonies where the numbering started at 92, as if those were the only ones that mattered!) And, when I was a kid, there were supposed to be 104 Haydn symphonies; now we think he wrote at least 107, but do we renumber all the later ones to accommodate the very early ones we found? Heck no!

Even more recent composers run into this problem. Bruckner wrote and published nine symphonies. But then, after his death, they found an early trial-run symphony that he wrote but never published, so they decided to call it Symphony No. 0 ("Die Nullte"). Then they found another one, so they called it (not Symphony No. -1, that would have been awesome), but Symphony No. 00.

And so it goes...


It's not so much that the choice of key was fundamental, it was more a case of identifying each particular piece, with the form being so similar in some cases. If Bach's friend said after a concert "I really liked that fugue", Bach may have said "You mean the Bb one?" It was so much simpler just to label them with keys anyway.It didn't happen all the time.Bach's preludes and Fugues were all done in different keys for a specific purpose, and as such were proudly named. We don't talk about 'Fur Elise in A minor', which begs the question - did a particular piece always get played in the same key? I suspect yes, as far as just tuning went then. A piece would have been written in a certain (stated) key, so readers would have to play it in that same key. I wonder what buskers did though.


In this case, these were pieces in a collection called "The Well-Tempered Clavier" And in this case preludes, fugues, simphonia and inventions were numbered according to their appearance in the collection and the key. "Invention #1 in C" "Prelude and Fugue No. 17 in A-flat major" for example. In these pieces, the exposition or main theme was presented in the main key and would then progress through several modulations ( or key changes) before arriving back at the home key signature at the end. There were literally dozens of similarly named works by the same composer in the same collection.

  • The famous "fugue in g minor" isn't from the Well-Tempered Clavier. Jul 17 '14 at 18:54
  • One thing I would add: In Classical music before the Romantic era, the rules were fairly strict. For a piece to actually be over, you needed to have a PAC in the key of the piece; if you have a pickup of 1/8 note at the beginning, then there will be 1/8 note missing in the last bar. Compared to modern music, you can start in one key, head to another and end wherever you like. So naming a piece with the key in there made a little more sense back then. Jul 17 '14 at 18:54
  • Ah. It has been a long time since I studied Baroque music, but it does not surprise me I got that bit wrong.
    – Hal H
    Jul 17 '14 at 18:58
  • @Basstickler - that's quite a sweeping statement, about the perfect authentic cadence. I'm pretty sure that a lot of pieces from the Classical era did not use this. A lot used the perfect cadence (V-I), but that's not the same. The anacrucis part is inconsequential.
    – Tim
    Jul 18 '14 at 9:33
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    @Tim - I suppose I haven't analyzed enough pieces to speak on it from personal experience but all of my schooling led me to believe it was the case. Either way, I would feel safe saying that the piece had to end on the tonic, so for the purpose of this question, the key had more importance than more modern pieces and often defined parts of a piece. Do you mean to say that the anacrusis piece is inconsequential to the question? If so, I mean to say that there were lots of 'rules' that were supposed to be followed, and the pickup is another example. I could see that being confusing now. Jul 18 '14 at 16:52

Short answer: It's a convenient way to identify pieces that were typically not given other titles.

More involved and Bach-specific answer: Choice of key was an important part of the composition for two reasons (with the first being much more important):

  1. Different keys had different tunings and hence sounded different before the widespread use of equal temperament.*
  2. Certain keys are easier or more difficult for keyboard players to play in.

Furthermore, Bach didn't name his pieces. In autograph manuscripts they are simply given numbers in sequence, a tempo indication, and how many voices are in the fugue or nothing at all. He was certainly aware of what key he composed any given piece in, but I don't know that was more important to him than the fugue theme, tempo, or any other characteristic.

Even after equal temperament had become the norm composers continued to label pieces by key. This was probably done again out of convenience and tradition. In addition, keys tended to keep certain characteristics culturally even after their actual sound differences were lost through equal temperament. Well-versed composers were aware of this 'key culture' and I believe continued to connect their serious compositions to its ethos.

*Contrary to popular misconception, well-tempered doesn't mean our modern system of equal temperament.

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