Abstract: An automatically operated tuning indicating system for the preliminary tuning and for retuning during the performance of a set of timpani drums or other percussion-type instrument having a tunable resonating body cavity is provided. Automatic indication of tuning is achieved substantially in silence or at very low sound levels without requiring the production of an audible level of sound that could be readily detected by or distracting to persons in an orchestra other than the timpani player during the tuning and/or retuning. Tuning and/or retuning during a performance is under the visible control of the timpani player both as to which kettle drum of the timpani set or other musical instrument is being tuned and the extent of the tuning.