“You have to learn to do nothing.” —Pepe Romero
Watching legendary guitarist Pepe Romero teach tremolo was a revelation to me. One of his key points about finger movement in tremolo is timing the reload or return of a after m plucks (as if a and m were alternating) and not after i. As he explains the motion, the movement from a to the string is deliberate or active and from the instant after a plucks our attention moves to m while a unconsciously or passively relaxes. Essentially, the act of doing nothing releases a back to its place to ready for its next stroke. This is counterintuitive, as it would seem more natural to let a remain flexed after m due to the basic sympathetic motion of the fingers. But it is precisely in the case of tremolo that developing independence between a and m, and timing their return, can lead to a better sense of both rhythm and overall movement.
Of all the techniques in Mastering Tremolo, focusing on timing the return of a, even for a little bit, has been most helpful to me in evening out my tremolo and reining in the gallop that often occurs into the next beat when playing at high tempos.