Timepiece assembly, comprising: - a mechanism, - a mechanical resonator suitable for oscillating along an oscillation axis about a neutral position corresponding to the minimum potential mechanical energy state thereof, - a device (8,10,12) for maintaining the mechanical resonator forming with the latter a mechanical oscillator for defining the working rate of the mechanism, each oscillation of the mechanical resonator exhibiting two successive alternations between two end positions on the oscillation axis defining the oscillation amplitude of the mechanical oscillator, - a device for regulating the frequency of the mechanical oscillator, this regulating device comprising an auxiliary oscillator, a device (26,60,62) for applying regulation pulses to the mechanical resonator and an electronic control circuit (58, 58A) suitable for generating a control signal which is supplied to the regulation pulse application device for the activation thereof, - a sensor (24, 34) suitable for detecting the passage of the mechanical resonator via at least a certain given position on the oscillation axis; the regulating device also comprising a measuring device (50, C2) suitable for measuring, on the basis of position signals supplied by said sensor, a time drift of the mechanical oscillator relative to the auxiliary oscillator; the timepiece assembly being characterised in that the regulation pulse application device is formed by an actuator (36, 76, 78, 86)suitable for generating, in response to the control signal which is dependent on the time drift measured, mechanical braking pulses applied on a braking surface of the mechanical resonator, particularly at least one mechanical braking pulse applying a certain braking force on this braking surface, when at least a certain time drift of the mechanical oscillator is detected; and in that the braking surface has a certain extent along said oscillation axis and is arranged in such a way as to enable the application of said mechanical braking pulse with the triggering thereof at a certain given time during an alternation, regardless of the oscillation amplitude of this mechanical oscillator in an amplitude range having a certain extent and corresponding to a usable operating range of the mechanical oscillator, said given time being selected such that the passage via the neutral position of the mechanical resonator does not occur during said mechanical braking pulse. - a mechanism, - a mechanical resonator suitable for oscillating along an oscillation axis about a neutral position corresponding to the minimum potential mechanical energy state thereof, - a device (8,10,12) for maintaining the mechanical resonator forming with the latter a mechanical oscillator for defining the working rate of the mechanism, each oscillation of the mechanical resonator exhibiting two successive alternations between two end positions on the oscillation axis defining the oscillation amplitude of the mechanical oscillator, - a device for regulating the frequency of the mechanical oscillator, this regulating device comprising an auxiliary oscillator, a device (26,60,62) for applying regulation pulses to the mechanical resonator and an electronic control circuit (58, 58A) suitable for generating a control signal which is supplied to the regulation pulse application device for the activation thereof, - a sensor (24, 34) suitable for detecting the passage of the mechanical resonator via at least a certain given position on the oscillation axis;