Tempo

Tempo is musical terminology for music speed. Tempo describes the pace or speed at which a piece of music is played. Tempo can be an exact measure of the interval of beats in a piece of music (aka bpm), or it can be a descriptive label such as slow or fast paced, or, as with classical Italian terminology, help to describe and convey how a piece of music should be presented and emoted by the musician, ie "Allegro" meaning cheerful or "Presto" meaning quickly.

Music Speed Changer iOS tempo controls explained