I have been reading an orchestration book written by English author Gordon Jacob in 1962.. In his book he states "The B Flat clarinet is used for flat keys and the A Clarinet for sharp keys. And yet, I see many musical examples in RK's book where he uses a B flat clarinet in sharp keys and vice versa for the A Clarinet. Is there a consistent usage for these two instruments in sharp and flat keys? Thank you
I've never read Jacob's book, but my guess is that he's referring to the concert key, not the written key for the clarinet. For example, D major is a sharp key, so you'd probably want to use the A clarinet, but because of the way the transposition works, the A clarinet will have the signature of F major (one flat). Similarly, F major is a flat key, but the Bb clarinet will have the signature of G major (one sharp).
Basically, the rule is this: use whichever clarinet makes for the easier key signature.
Concert A major (3#): 5# on Bb, 0 on A. Use the A.
Concert Eb major (3b): 1b on Bb, 6b (or 6#) on A. Use the Bb.
A couple of caveats:
1. The A clarinet is really only used in classical music. If you're doing jazz arrangements or similar, always use the Bb clarinet even if the key signature is weird. I believe the same applies to concert band music; can someone confirm this?
2. Since the A and Bb clarinets have the same written range (down to written e), the A clarinet can play concert c# as its lowest note, while the Bb clarinet stops at d (as, unfortunately, does GPO Lite's clarinet). So if you need the concert c#, you'll have to write for A clarinet no matter what the key is.
3 [added after first posting]. The A/Bb choice currently only exists for the most common size of clarinet. In some older orchestration books, you will see mention of the bass clarinet in A and of the (small) D clarinet; in fact, Wagner and Richard Strauss wrote for these instruments as tonality demanded (there's a famous D clarinet solo in Till Eulenspiegel). These instruments are no longer used, even in professional orchestras; their places have been taken by the bass clarinet in Bb and the Eb clarinet respectively. The Bb bass clarinet, however, now has an extension so it can play the lowest note on parts written for the A instrument (actually, the extension often goes lower still, so that the instrument can play bassoon parts). I don't know if the same is true for the Eb clarinet, but the low register of that instrument is so little used that I can't imagine that it would make any difference.
Last edited by marnen; 06-05-2006 at 11:32 PM.
Reason: A little more info.