Ronan Guilfoyle's clinic on rhythm at the 2006 IAJE changed my entire perception of rhythm, time and how to practice it. The whole clinic - from dissecting two classic Trane solos from the perspective of feel, the "Zen metronome" exercises, and the idea of "the rhythmic being" outlined in this blog post - revitalized my practice regimen and focused my sense of how to hear and develop time. Recently, I've been working more out of drum books and applying certain drum or percussion grooves into my comping; and in playing with different drummers, in different styles, I've found that this kind of study greatly affects my interaction with drummers and how I play as a whole.
Time and time feel (or groove) are two very different things, but equally important. To establish a personal, internal sense of time, a metronome is an invaluable aid. Practicing at slow tempos in accurate time has led to my most marked improvements in technique and facility at the instrument. Stanton Moore's exercise of playing "in the cracks" - a steady stream of 16th-notes that gradually move from straight to swung and back again - done with a metronome has made my ear attuned to how drummers inflect a groove on the hi-hat or ride. And it's that kind of rhythmic simpatico that is so crucial to all great music - the way chamber ensembles phrase together, the way a great classical soloist knows where and how to play rubato, the way the great rhythm sections (from Garland/Chambers/Philly Joe to Neville/Porter/Zigaboo) hook up, the characteristic swing of a batucada or of a Dilla beat. And maybe a metronome isn't necessary if one's ear is attuned to that rhythmic sense via practicing with records, or an innate sense of time. But for me, a metronome has been a terrific aid in refining my personal sense of time, combined with an attention to rhythmic detail.