I never learned theory until I started playing with Rick a couple of years ago, and kick myself for having waited for so long. It is immensely helpful, and handled properly, helps to get the structure of songs, scales, and so on, into one's head. The tough part is finding a decent book (Edy's Music Theory is pretty good, but even so). For example, I recently figured out what the V7 of V, and the II and VI of V were, and lo and behold they showed up in practically every song I have been working on. It is very clarifying. It also is very helpful in helping you remember the chords of songs, because you can anticipate where things are going to go, substitutions, etc. yours, Peter T.