A few random comments.

m7(b5) is far more common than #5 and is called a half-diminished chord.

A 2 chord in BIAB is used for several chords: add2, add9, and as noted, sus2. However, in pure music theory sus2 is rather discouraged as it is not really a suspended chord in the sense that, where does it resolve? But I know this will start an argument so never mind. If you look at the file pgshortc.txt you will see how BIAB uses the 2 chord. ps I do not agree.

A 6/9 chord is one of the most magical sounds in the world when played on a Bossa Nova acoustic guitar. Musically it is in the same grouping as a major triad and major seventh, in the sense that jazz players use these three interchangeably.

Finally, while a 7alt chord is a jazz staple, you May find it as the final chord in a four or eight bar phrase in pop songs. The ‘alt’ means altered. That means that the fifth is not perfect and the ninth is not major. Thus the chord may have any combination of flat or sharp 5, and / or flat or sharp 9.

Hope that helps.

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; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.