A triplet is a group of three notes played in the same time as two notes of the same kind.

A bar of eighth note triplets in 4/4 (which is really 12/8) could be counted:

1 2 3 2 2 3 3 2 3 4 2 3

An easier way to count this is:

one and a two and a three and a four and

This triplet pattern is from Example H2.

Triplets are often responsible for the creation of swing rhythms when the first note is carried over to include the length of the second note. This produces an uneven grouping of notes where one crotchet (quarter note) is followed by a quaver (eighth note) so you get a long/short, long/short pattern. The following diagram indicates that a swing rhythm is required because of this grouping.

Duplets

Duplets are a similar rhythmical devise as triplets, but are used only in compound time signatures. Duplets indicate where two notes can be placed in the space of three of the same kind. In the following example it is only the piano which is playing duplets as the bass is playing each beat (dotted crotchets).