He played with heroin a lot, too..........
I know diddly about theory, but as far as Jerry's timing..........
I read Jerry's "favorite" time trick was to play 5 notes in the space of 4, so that over a few measures he became slightly out of sync with the "One" beat.
Also, the only hard/fast rule of the Dead in any incarnation has always been that one IS ONE!
Another trick of Jerrys was to play the melody straight the first time through. Then, he would deconstruct and sometimes play the melodies backwards or even sideways. Many times his single-and-double note solos built to crescendos of chords.
Best example of this on record is "Morning Dew" from Europe 72.
Also, Jerry used analog echo A LOT and also dug using a very wet reverb sound. The Wolf, Tiger, Top Hat, etc, were all fitted with high-gain buffer amplifiers activated by Bourns push/pull knobs for that super-distorted sound like at the end of "Deal".
Like I said, I know dick about theory. What I do know I learned from watching and listening. I saw the Dead about 250 times and Jerry's band probably 50 times at least. If you study the Garcia's songbook you begin to realize that a lot of Jerry's tunes were based on simple, repetitive lines. If you don't get it this time, don't worry because it's coming around again. There's a helluva lot of bluegrass in Jerry's music, and to me Jerry was ultimately a blues player. He learned jazz chops from Merle Saunders, and would practice weird little runs that Merle had shown him or dropped in a jam and the next time Jerry saw Merle he would have it down pat.
Listen to "Crazy Fingers", "Brokedown Palace", and "Attics of my Life" for examples of what a melodic genius Jerry really was. The lyric of Crazy Fingers is almost Haiku, also the chorus of "Ripple" just misses being a perfect Hailu poem.
Another quick note---- Jerry was once asked how much influence he had on Hunter's lyrics. Jerry response was something along the lines of replacing consonants with vowels, because you can't sustain a consonant!!!
Jimmy Herring is doing one helluva job right now. Probably the biggest shoes in the biz to try and fill, in front of an audience that is at once forgiving and very demanding. Vince Welnick learned that lesson trying to take Brent's seat in 1990. If you're interested in hearing what the Dead can do, and I think Phil & Friends actually did it a couple orders of magnitude better, check out this site:
www.furthurnet.org
Or drop me a PM with your address and I'll send you some CD's of Phil, TOO, and Govt Mule that will blow your mind!