Regarding Cecil’s answer about why instruments come in different pitches (http://www.straightdope.com/classics/a1_319b.html)
I think he’s a bit off the mark here. As a classically trained trumpet player, I have a whole kit full of trumpets in different pitches. The reason why trumpets – and French Horns for that matter – come in different pitches has to do with the fact that they started out without valves. The pitches that early trumpets (Baroque and Classical periods) were able to produce was determined by the natural harmonic series that occurs when a column of air in a tube is set vibrating. Early trumpeters used their lips to select which pitches would be played, but there was no way to sound notes that did not occur within the harmonic series. This meant that they had to have trumpets in various pitches (i.e. various lengths) to play pieces in different keys. For example, you had a “C trumpet” to play works in C, a “D trumpet” to play works in D, etc. etc.
The invention of valves and keys changed this because it allowed trumpets and other instruments to play chromatically – i.e. in any key - without having to change instruments. This would seem to suggest that the invention of valves would have led to the use of a single instrument – pitched in C for example – which would be suitable for all music in all keys. That didn’t happen for a variety of reasons, but the one which I believe is relevant to the saxophone example has to do with pitch center and instrument range.
Cecil alludes to this when he writes “…if you think a tenor (B-flat) sax is too low for a given tune, you can get an alto (E-flat) sax instead.” But this explanation does not address why B-flat and E-flat were chosen as the pitch centers for these instrument (why not B natural and E natural?)
Every instrument has a limit as to the number of notes – it’s range – that can be played on it. The range is centered on the pitch the instrument naturally sounds (i.e. what pitch the instrument is “in” – C, B flat, E flat, D etc.) In the case of saxophones, I believe that the pitches of the different kinds were selected to provide the maximum possible range within a given voicing. For example, a baritone sax is able to play a certain range of notes centered in the “baritone” voice register. Some of these notes overlap with the lower end of the tenor sax range, but the tenor can play higher, overlapping with the lower range of the soprano sax which can play higher still. Altogether, the saxophone family – from contrabass to sopranino - pretty much covers the entire range of the piano, which pretty much covers the “useful” range of pitches used in music.
A final note: Cecil wrote: “Changing keys would mean having to completely rethink your fingering” Not exactly, at least in the trumpet world. The are two ways to solve this problem. The easiest is to re-write the music – transpose it up or down - so that the pitches sounded correspond to the notes desired. In this case, your changing the written notes, not the fingerings (i.e. C is still fingered C, but you write a D instead of C and the musician plays a D, but it sounds at the pitch you want to hear).
The more complicated way – something that trumpet players do all the time – is to play a note different from what you see written (called transposing). We don’t think of it as “re-thinking the fingerings”. Instead, we play notes above or below the notes that are written. For example, you have a B-flat trumpet in hand but your music is for trumpet in C. You have to transpose every note up a whole step. You see a C but you play a D (different fingering). You could argue that the trumpet player has changed the fingering of the note C, but most trumpet players would tell you that they really haven’t. They’re just playing different notes. C is still C, but although I’m seeing a C on the page, I’m not playing C, I’m playing D. See?