raking: Striking a string with one finger and then striking the next lower string with the same finger.

relative tuning: A way of tuning the guitar to itself so that you don’t need any outside reference pitch.

repeat sign: In musical notation, a combination of one thick and one thin vertical line with two dots that tells you that you repeat some portion of the song.

rest: Any time during a musical piece in which no notes are being sounded.

rest stroke: A right-hand stroke — unique to classical music — in which you pluck straight across (not upward) the strings so that your finger lands, or rests, against the adjacent lower-pitched string.

rhythm: A regular pattern of beats or pulses in music.

rhythm slashes: An indicator in guitar notation that uses slash marks (/) that tell you how to play rhythmically but not what to play.

rollers: The tuning posts on a nylon-string guitar that uses a slotted headstock.

rubato: Musical phrasing and timing that is governed by the musician's musical ideas instead of by the strict adherence to a set tempo.