Originally Posted By: Lee N
Just remember, key signature is a notation thing only - it does not relate necessarily to the home key.

This is quite important and I think Lee N may well have identified a confusion.

The key signature identifies the "home key" for the song and gives a short-form indication of how to identify the notes as they're written on the staff. For example, if the key signature is BbMaj, then the there will be three flats at the start of the staff and the reader will know that notes on the B, E and A positions are to be played as Bb, Eb and Ab. Many songs will modulate to a different key for a while, then return to the home key, and during those parts the reader will see that as notes on the staff start to get individual sharps, flats or naturals, which will remain for the duration of the bar or until another sharp, flat or natural.

It unusual to change the key signature for that. It's normal that those sharps, flats and naturals indicate the modulation -- the temporary key change.

As an example of this, it's perfectly possible to write any song with a CMaj key signature and mark all accidentals as they're used in the song. Some people prefer to work that way and there is no reason why they should not do so.

I don't tend to write chords using the Nashville/Roman notations, but just to see what BiaB does, I tried typing #IV and #V7 into cells and saw the F# and Ab7 that I would expect. For my own benefit I also tried iii7 and iiim7 to check how major and minor thirds are handled.

Jazz relative beginner, starting at a much older age than was helpful.
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