Abstract: Apparatus for turning a strobe wheel to assist in tuning a musical instrument. The apparatus features side-by-side rotary shafts, including a driving shaft and a driven shaft--the former having uniform outside diameter along its length, and the latter having a taper along its length which taper is based on the mathematical formula that determines the intervals between successive notes in such an instrument. The driving wheel is turned at selected substantially constant speeds. The driven shaft is turned through an endless band which couples the shafts. The latter-mentioned shaft is intended for driving a strobe wheel.