REGINA SPEKT0R
So this is something I've never fully understood. I understand that, with an alto saxophone for example, a notated middle C sounds like an Eb, however, I really want to know whether a transposing instrument can play in any key outside of its own? I mean, it can hit all the notes in a chromatic scale right, it should work in every key? What am I missing here?
Yes, any instrument which can play the chromatic scale can play in any written key.
When an instrumentalist looks at a piece of music, all they see is their part, right? With everyone playing the same music, in the same key you would think they're looking at the same key signature. But! The alto sax -- an Eb transposing instrument, as you pointed out -- sees a different key signature from the Bb clarinet, or the trombone. Yet they all sound harmoniously. This is because the sounding note is lower than the written note. It's hard to put it into this post but:
[high squeaky voice]:
Written!
.
.
.
.
.
.
.
[low grumbly voice]:
Sounding!
While the actual transposition may not be this drastic, it certainly helps ya remember which way they go! (Ceding
very few exceptions, like the piccolo.)
In bygone times, there were not as many buttons/fingerholes on all instruments to allow for the chromatic scale, simply because the mechanisms for extended reach had not yet been developed. Players would switch between instruments (or add coils/tubing) as necessary. Thus why the same instrument came in several keys. As the instrument evolved and gained the full chromatic scale, this became unnecessary. But why do we still have Bb soprano sax, Eb alto sax, Bb tenor sax, Eb clarinet, Bb clarinet, etc? Dunno that one. (I think it's so you don't have to learn new fingerings for a lower-pitched instrument in the same family, but don't quote me on that.)
Basically: history started it, and it's stayed that way. Now, the key of the instrument refers to its size and register rather than the key(s) in which it can play.