The present paper describes a corpus-based singing voice synthesis system based on hidden Markov models (HMMs). This system employs the HMM-based speech synthesis to synthesize singing voice. Musical information such as lyrics, tones, durations is modeled simultaneously in a unified framework of the context-dependent HMM. It can mimic the voice quality and singing style of the original singer. Results of a singing voice synthesis experiment show that the proposed system can synthesize smooth and natural-sounding singing voice.