A sequencer that uses digital circuitry to perform all of its functions and to generate all of the information it outputs. Sequencers with digital memory first appeared in the 1970s (the canonical example was the EMS Synti-AKS with its microprocessor-controlled sequencer built into the case lid), and these quickly evolved to be able to store longer and more complex patterns as well as additional performance information. The original designs were usually capable of storing a sequence of notes that was relatively short but still much longer than than what the analog sequencers of the day were capable of, but they were usually strictly "monophonic" in that they could output note data for only note at a time. Methods for synchronizing to external clock sources ware also lacking.