A sequencer is an electronic instrument that can be used for recording and storing sounds so that they can be replayed as part of a new piece of music.
sequencer in British English
(ˈsiːkwənsə)
noun
1.
an electronic device that determines the order in which a number of operations occur
2.
an electronic device that sorts information into the required order for data processing
3.
a unit connected to a synthesizer, which is capable of memorizing sequences of notes
sequencer in American English
(ˈsikwənsər; ˈsiˌkwɛnsər)
noun
an electronic device or software program that allows a sequence of musical sounds, recorded in digital form, to be altered before being played back