A method for extracting fundamental frequencies from a mixed tone perfomed by natural instruments is proposed. Acoustical features are assumed in this study : (1) Low-order harmonics have greater powers than other partials, (2) powers of harmonics are continuous in time, and (3) the power spectrum for a mixed tone can be approximated by summing the power spectra of each tone. The “fundamental-ness” of the partials is introduced by these features. Duet and trio tones performed by natural instruments are used as test tones. The averages of the correct identification rates evaluated by performed musical notes are 84%-96% for duet tones, 80%-87% for trio tones.
