Yeah, It would be alot easier if it was that way. A at 440hz is what is called "concert pitch". Not all instruments are in concert pitch, like Saxophones, trumpets, and clarinets.

Here they are:

Bb Clarinet: notes sound a Major second lower.
A Clarinet: notes sound a minor third lower.
Eb Alto Sax: notes sound a major sixth lower.
Bb Tenor Sax: notes sound a major ninth lower.
Eb Baritone Sax: notes sound an octave plus a major sixth lower.
Bb Trumpet: notes sound a major second lower.
C Trumpet: sounds as written.

Josh, I looked up the issue about the trombone and my sources say it is in concert pitch. Let me know if you find anything different. Latr