FACTUAL REFERENCE
PINS, DRUMS, AND CYLINDERS

Pinned barrels and cylinders provide a straightforward method of sequence control.
As the cylinder rotates, pins at selected positions lift or trigger mechanisms.

This pattern appears naturally in mechanical music and other automated devices:

ROTATION = TIME AXIS
POSITION AROUND CYLINDER = WHEN
POSITION ACROSS CYLINDER = WHICH ACTION
PIN PRESENT = TRIGGER

That is wonderfully legible machine logic. You can often SEE the program.

A digital sequence may be invisible without a debugger. A pinned drum can put the
entire performance on a rotating piece of hardware in front of you.