Welcome to the forum, Corinne.

Are you sure CMaj7b5 doesn't work? What version of BIAB are you using?

As another alternative, the b5 and #11 are the same pitch, different octave, and CMaj7#11 is not supported, but you can also use CMaj9#11. And if the CMaj9#11 sounds OK for you, you can program a shortcut so that you get that when you enter CMaj7#11. If you want to know how to make shortcuts, write back.

I see you have made two posts, the other about D2 in the French forum. My French isn't up to the task any longer (although John's certainly is), so if you post that question here I'm sure we can comment.

Mario has a good point, it would be nice to be able to create our own chords, but they would only work for MIDI. Real Tracks would have to use substitute chords, and BIAB would need to be told what they are.

BIAB 2026 Win Audiophile. Software: Fender Studio One 8, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Fender Quantom HD8 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.