The only concrete example of min (add9) chords in popular music that I could find was Every Breath You Take by The Police. It’s usually far easier to grab a min9 chord on the guitar, but the the add9 version has its own sound and actually seems to convey more tension to my ear. It’s also a good chord to get the fingers used to less familiar locations on the fretboard without making any extreme stretches.
Maj (add9) Chords
Major Add 9’s are great chords without being overly complex. The triad on strings 2/3/4 plus the 9 on the top string is a personal favorite, as is the movable form of the open C (add9). The root-3 version is really more of an inverted Mu (1/2/3/5) chord which I’ll dig into later.
6/9 Chords
This one is quite uncommon in rock or pop but easy to find in jazz where it’s usually used as a more interesting tonic chord. The only obvious place I could find this in the rock world was America’s Horse With no Name where the second chord of the main vamp is a 6/9. Interestingly, this chord contains the entire major pentatonic scale and is also a set of stacked fourth intervals, meaning you can play a whole barred figure at any fret and technically be playing a 6/9 chord with the root on the third string. I’d think you’d want a strong bass note behind the guitar to make that work. I haven’t tried it, but I thought it was interesting enough to include.
Pedal On 