CrossRoads:
you can use keypad.h library to read a 72 key keypad.
[Snip]
Multi-press, that would be managed in your sketch.
Actually, the keypad library has been multi-press capable since July of last year. I didn't make an announcement yet because I was hoping for a relatively slow testing period. But it's posted and I'm working with someone right now who is implementing a full multi-press (a.k.a. n-key-roll-over, nkro) keyboard. As soon as I get a report from him I will upload the latest fixes (the last key wouldn't report that it was released). Shouldn't be more than a day or so.