In this paper, the content-based retrieval of audio example based on MP3 digital music archive is considered. In our proposed method, the sub-band coefficients (SBC) in a MP3 frame is used for feature extraction. Both quantization-tree indexing (QT) approach and the melody-line tracking (MLT) approach are proposed for indexing MP3 objects. Finally, a two-stage comparison method is used to measure the similarity between MP3 objects. We also employ the measurement of the similarity between query sample and database items. Evaluations on a content-based MP3 retrieval system are performed. Experimental results show that our proposed approach can achieve good performance and high accuracy