I have also been annoyed at how BIAB transposes. I play saxes and see some weird progressions when I transpose the lead sheets. I have been figuring out the rules that BIAB uses for transpositions, with the intention that I will offer some suggestions for improvements in the wishlist section.

Here are the transpositon rules that I have observed when transposing for Eb Alto. What I did was write chords in concert key on every step of the chromatic scale, using both sharps and flats for the "black keys". Then I transposed the notation for alto sax, and then transposed the key of the song to every possible major key.

1. Whether a chord root is a sharp or a flat depends on the key that you are transposing to.
- a. Chord roots go by the key signature of the new key.
- b. If the chord root is not in the new key, BiaB prefers flats, with the following excetptions.
- c. Exception 1. If the new key is C, G, D, or A, then add a sharp to the key signature to predict what roots will be flats or sharps. -- Don't do that for the key of E, there will be a Bb instead of A#.
- e. Exception 2. In the key of F, there will be an F# instead of Gb.
2. If a note or chord root can be written as a natural instead of a sharp, flat (or double sharp or double flat) it will be. Therefore a IV chord in Gb will be a B rather than a Cb, and an E#mb5 will always be written as Fmb5.
3. BiaB does not like the key of F# -- it gives you Gb instead. Combine this with the rule above and you get interesting results when you have a IV chord. So, if a piece is in the concert key of A, and you transope for Alto sax you get key of Gb, and when you have a I-IV-V progression, the music will switch from mostly flats for the I and V chords to mostly sharps for the IV chord.

Things that BiaB does not take into consideration when transposing:
1. Spellings of notes in chords. Many of the chords BiaB chooses contain double sharps or flats. It would be nice if there were different cut-off points for naming non-scaletone chords in order to avoid double sharps and flats in the chord tone spellings. Flats make more sense for roots of augmented chords, and sharps make more sense for diminished chords. Major and minor are in between.
2. BiaB does not recognize keys of the moment. Therefore a ii-V-I in a temporory key could be written partly as chords containing sharps and partly with flats.

I hope this is helpful to someone. I'll have to wait to another day to write up my wishlist ideas. I should have gone to bed a couple of hours ago, but wanted to share what I learned about BiaB's tranposing rules first.

Jim