The PD7759 is an external ROM type speech synthesis LSI employing the waveform coding method. In addition to the ROM capability of up to 1 Mbit, the PD7759 realizes the synthesis of speech sounds of any length by using the ADPCM data transferred from an external ROM. As the synthesizing method, it adopts the ADPCM method and the PCM + waveform element method. The ADPCM method is suitable for synthesizing clear and natural speech sounds, and the PCM + waveform element method is for the synthesis of sound effects and melodies. And by using them together, the