The tremolo technique is used to create the illusion of a constantly sustained melody both in classical guitar music and in flamenco. However there are slightly different approaches to playing tremolo in either style. Generally, classical guitar music uses a free stroke with the thumb followed by three repeated notes on the treble strings, resulting in a four-note group. In flamenco the thumb uses a rest stroke on the bass strings and four notes are used on the treble strings, resulting in a five-note group.
The best way to practice tremolo is first to play slowly while aiming for an even sound. By learning to control the fingers at slow tempos, evenness and clear articulation of the notes can be achieved. Then when the playing speed is increased you will produce a smooth melodic line.
There is a clear connection between the hand movement used in tremolo and arpeggio playing. Working to improve arpeggio playing will help to control the fingers of the right hand.
Finally, try practicing p–i–a–m–i on the first string. This one-string tremolo will help you observe the range of your finger movement. Practice slowly while aiming for small controlled movements. This is the key to developing a great tremolo technique.
Try the following exercises, which build from a three-note to a five-note tremolo. Notice there are several different right-hand fingerings that are usable.
Here’s a five-note tremolo demonstrated slowly and then at a medium speed.
And finally, here’s a fully-formed tremolo. Try this one as a four-note group as well.