Abstract: A function generator (25) receives the signal (svm) representing the speed of rotation of a motor (13) and works out EN=CN+f (vm), f (vm) being a single-valued and monotonic function of the real speed vm of the motor and CN being worked out by computer means (24) so that: CN=EN-f (VM), VM being the nominal value of the speed of rotation of the motor. The latter is fed by a signal which is a function of EN. The reference information f (VM)=IC is worked out from an item of error information which is a function of the deviation between the real speed (vb) and reference speed (vp) of a tape (10) driven by the motor, the rate of variation of IC having a maximum value limited in absolute value.The device is suitable for subordinating the rate of travel of a tape carrying sound to the frequency of a pilot signal.