A musical tone generating apparatus, which is capable of effectively utilizing the access timing for an unused slave sound source, is provided.The musical tone generating apparatus is composed of a master sound source 1000, which comprises a mode switching means 101, an accumulator 102, an upper-address processing means 103, an address memory for a second sound source 104, an address-switching output means 105, a waveform data register 106, a sample buffer 107, an interpolation coefficient memory 108, an interpolation coefficient extracting means 109, a sample interpolation means 110 and a selection means 111.