Decuplet
A rhythmic figure of ten equal notes in place of the regularly expected subdivision of a note.
What it means
A decuplet is a rhythmic figure created by dividing a beat note into ten equally long, smaller notes. It belongs to the group of irregular rhythmic groupings, known as tuplets, that deviate from the usual duple or triple subdivision.
In the notation
In the score, the ten notes of a decuplet are usually grouped by a beam or bracket and marked with the number 10. This makes clear that the group as a whole lasts exactly as long as the regular subdivision of the underlying note, such as a group of eighth notes, even though the number of notes differs.
Musical use
Decuplets are rare and appear mainly in virtuosic piano and orchestral literature of the 19th and 20th centuries, where composers wanted to notate especially fine, flowing ornamental figures or tonal effects. They require precise counting and a confident rhythmic feel from performers to fit the ten notes evenly into the given time span.