Another point. Writing a standard 9 chord like C9 assumes the 7th. Using Add2 means no 7th and of course the 2 is the same as the 9.

Folks with no theory training think of chords as linear like a C9 goes C, E, G, Bb and D. But in the real world a C9 can routinely be written as Bb, D,and G which could easily be looked at as a Bb6 which is why the key sig and bass note are important.

Then if the dominant 7 (Bb) is clashing with the melody but you do want the D then it's written as Add2. The 2 can be lower like C, D, E, G or higher like E, G, C, D both with a C in the bass and no 7th.

Whether or not you play the bass note depends on who you're playing with. If it's solo piano or guitar then of course you play it but if you have a bass player it's not needed so you can concentrate on the inversions.

Good questions and welcome to Theory 101. Biab actually does a pretty good job in following these concepts which is why it does the Add 2 and the Sus that way and is also why it's a decent theory teacher if you take the time to find out why it does things like this. Music is way too complex and different folks have different (and valid) opinions on some of this stuff but Biab is pretty good for what it is.

Bob

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