noun

1. Any device that activates or deactivates the components of a machine or system according to a preplanned sequence (as in a washing machine, or central heating system).

2. A device or system that orders and/or modifies digitally stored music and sound for playback.

   “a MIDI sequencer”

3. A device for determining the sequence of monomers in a polymer, especially amino acids in protein, or bases in DNA; A sequenator.