A composite oscillator for producing an oscillator signal suitable for use as a clock source, the oscillator signal having an oscillator signal frequency, the oscillator signal frequency having a reduced sensitivity to acceleration, the sensitivity to acceleration being defined by three, mutually orthogonal acceleration sensitivity vectors, the composite oscillator comprising: two piezoelectric crystal resonators (42, 44; 106, 108; 200), each said resonator having an active resonance region defined between a set of electrodes (100, 104; 202) capable of receiving, by electrical coupling, signals caused by oscillator resonance in said active resonance region during operation of said oscillator, each of said resonators (42, 44; 106, 108; 200) being mounted in said oscillator using a cantilever mounting arrangement including one or more mountings, each resonator comprising an elongate member having first and second ends, the second end being opposite to said first end and a longitudinal axis extending between said ends, each respective resonator being asymmetrically mounted in said cantilever mounting arrangement in that the first end of each respective resonator is mounted to a substrate via said mountings and the second, opposite, end of each respective resonator is free, the asymmetry of said mountings with respect to each active resonance region defining, for each active resonance region, a dominant, relatively large, acceleration sensitivity vector, aligned with the longitudinal axis of the respective resonator, and relatively small acceleration sensitivity vectors which are mutually orthogonal and orthogonal to said dominant acceleration sensitivity vector, wherein said resonators are mounted in said oscillator to direct the respective dominant acceleration sensitivity vectors in substantially opposite directions so as to reduce the sensitivity of the oscillator signal frequency to acceleration. two piezoelectric crystal resonators (42, 44; 106, 108; 200), each said resonator having an active resonance region defined between a set of electrodes (100, 104; 202) capable of receiving, by electrical coupling, signals caused by oscillator resonance in said active resonance region during operation of said oscillator, each of said resonators (42, 44; 106, 108; 200) being mounted in said oscillator using a cantilever mounting arrangement including one or more mountings, each resonator comprising an elongate member having first and second ends, the second end being opposite to said first end and a longitudinal axis extending between said ends, each respective resonator being asymmetrically mounted in said cantilever mounting arrangement in that the first end of each respective resonator is mounted to a substrate via said mountings and the second, opposite, end of each respective resonator is free, the asymmetry of said mountings with respect to each active resonance region defining, for each active resonance region, a dominant, relatively large, acceleration sensitivity vector, aligned with the longitudinal axis of the respective resonator, and relatively small acceleration sensitivity vectors which are mutually orthogonal and orthogonal to said dominant acceleration sensitivity vector, wherein said resonators are mounted in said oscillator to direct the respective dominant acceleration sensitivity vectors in substantially opposite directions so as to reduce the sensitivity of the oscillator signal frequency to acceleration.