I don't think I would use #2 as a definition of "key", unless you mean using chords, melody and harmony to determine a key signature. But --

For #1, how it works depends on which version of BIAB you have. If it's 2015, there is an icon for key in the upper center of the screen. It presents two nifty sliders, to transpose when changing the key signature (left-hand column), or not (right-hand column). Older BIAB versions just work like the left-hand column does now.

Transposing instruments (trumpet, sax, etc.) are handled in one of at least two ways (that I know about), to deal with your #3 and #4. Preferences, Display, Transpose Options is the one I use. The song plays in concert key and displays notation in the key needed for the transposing instrument, so both can sound correct when played together.

I recommend not using Preferences, Transpose because you can forget you did it. I think there are a few other ways to transpose but I don't use them.

Did that help?


BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Presonus 192 & Faderport 8, Royer 121, Slate VSX, Adam Sub8 & Neumann 120 monitors.