Electroacoustic resonating apparatus capable of generating resonances of tunable frequencies. The apparatus includes two transducers coupled to a ferrimagnetic substrate at opposite ends thereof. The first transducer converts an input signal into a signal that produces bulk acoustic waves in the ferrimagnetic substrate. The second transducer receives the bulk acoustic waves and converts them into electrical signals, or alternatively a single transducer which performs both input and output functions. Variable magnetizing means located proximate to the ferromagnetic substrate induces a magnetic field throughout the substrate wherein the magnetic field alters the frequencies of the resonance of the acoustic waves. By varying the magnitude of the magnetic field, the frequencies of the resonances may be varied, thereby allowing tuning of the apparatus.