This paper describes drum sound identification for polyphonic musical audio signals. It is difficult to identify drum sounds in such signals because acoustic features of those sounds vary with each musical piece and precise templates for them cannot be prepared in advance. To solve this problem, we propose new template-adaptation and templatematching methods. The former method adapts a single seed template prepared for each kind of drums to the corresponding drum sound appearing in an actual musical piece containing sounds of various musical instruments. The latter method then uses a carefully-designed distance measure that can detect all the onset times of each drum in the same piece by using the corresponding adapted template. The onset times of bass and snare drums in any piece can thus be identified even if their timbres are different from prepared templates. Experimental results with our methods showed that the accuracy of identifying bass and snare drums in popular music was about 90%.