Why are some musical instruments made in different keys? If the tenor saxophone, a B-flat instrument, and the piano, a C instrument, both play the note C, they would in fact be producing different tones. The tenor saxophonist would have to transpose to D for the instruments to be sounding the same tone. Why don't they just build instruments so that a C (or any other note) is the same tone for all instruments?
Illustration by Slug Signorino
Before we get into this, Bob, let me explain to the befuddled masses what we’re talking about here. First of all, the true C is the same tone on whatever instrument it is played, namely 263 cycles per second. However, a true C is not necessarily called C on all instruments. On a tenor saxophone, which is known as a “transposing” instrument, everything is shifted down a tone (well, actually a tone plus an octave, but let’s not quibble). That is, if you play a “C,” you actually get a B-flat; if you play a “G,” you get an F, and so on.
The reasons for this have to do with the difficult nature of the sax. On instruments with a linear arrangement of notes, such as a piano, transposing keys is easy–you just shift your fingers up or down the keyboard. On instruments like the sax and the cornet, however, the notes are obtained by various combinations of valves scattered all over the instrument. Changing keys would mean having to completely rethink your fingering. To avoid this difficulty, saxophones are made in a number of different ranges, soprano, alto, tenor, and baritone being the most common. Essentially, instead of your doing the transposing, the instrument does it for you. Thus if you think a tenor (B-flat) sax is too low for a given tune, you can get an alto (E-flat) sax instead. Using the identical fingering, you’ll find the melody comes out about a half-octave higher. For ease of nomenclature, when sax players talk about playing a “C,” they are talking about a particular valve combination (which is the same for all saxes), not the actual tone that is produced.
Most saxes today are either E-flat or B-flat, but years ago there were also C and F instruments, the former being called a “melody saxophone.” Although it enjoyed some popularity in the 20s and 30s, it is rarely seen today. When C saxophones were still used, it made sense to write all sax music as though C were the home key–after all, C is the easiest key to sight-read, due to the absence of sharps and flats in the signature. Also, when they first invented this system, it seemed pretty obvious that on a C sax a “C” came out C, on a B-flat sax “C” came out B-flat, and so on. Admittedly, now that C saxes are uncommon, it seems a little perverse to have to choose between a B-flat and an E-flat as the result of playing a “C,” but having known a few sax players in my day, I must say it seems only appropriate.
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