A shuffle beat is a rhythmic pattern based on uneven beat subdivisions in which a note is played on the beat and the next note is played on the last uneven subdivision of the beat, creating a "shuffling" rhythm. A shuffle pattern is simply a triplet pattern (3 notes per beat) with the middle triplet omitted. So if the pattern is counted:

 

1-trip-let, 2-trip-let, 3-trip-let, 4-trip-let, ...

 

the shuffle would be:

 

1- -let, 2- -let, 3- -let, 4- -let, ...

 

This creates a sort of syncopated feel, with a repeating pattern of long and short notes. Over the music we write that two eighth notes are equivalent to the triplet-based shuffle rhythm. Count the long and short notes as "1 a 2 a 3 a 4 a."