I can't get Band-in-a-box to play Minor Major 7 chords. Even if the chord is spelled mMaj7 it plays the minor chord with a 7 (and not the Major7). I got the newest version of the program.
Is this a bug ?

This may not get as much attention because it should be posted in the main BIAB user forum, two or three below this one. Are you using BIAB for Mac or Windows? Which version?

The program will play mMaj7 in MIDI with no problem in my experience (Windows, BIAB 2018, latest build).

If you are using RealTracks it’s possible the artist(s) didn’t record this sound in the particular track(s) you are using. It’s also possible it’s a bug if the genre really should have them. So, we need to know what RealTrack(s) you are using. We can try to reproduce the problem and report it to PG Music. Give us the name and number, please.

Also test by trying another RealTrack, even in a very different genre. Bossa nova tracks that I use do support this chord, essential in Brazilian music.