OK - so this is a little weird. Our drum and bugle corps is composed of G horns - they all play in treble clef. I play a Yamaha Bb marching baritone and I'm trying to transpose the music from a written treble clef to bass clef, and from G to Bb.
Of course the first problem was to figure out what comes out of the big end of the G horn - a written C actually comes out of the horn as a G, etc. OK, so then all I have to do is play a valve 1 & 2 G on my baritone and it should produce the same sound as a written C on a G horn, right? - TADA - it does.
Of course nothing is that simple.
Without getting into structures and minor thirds that I really don't understand, it appears that the key signature for the written music needs to change when I try to transpose the notes. For example, a written treble clef key of C appears to be transposed to a bass clef key of G, a treble clef key of Ab appears to be transposed to a bass clef key of Eb, etc. - it looks like I gain one sharp (or lose one flat) in the transposition. Do I have any idea what I'm talking about!!??