A musical piece typically has a repetitive structure. Analysis of this structure will be useful for music segmentation, indexing and thumbnailing. This paper presents an algorithm that can automatically analyze the repetitive structure of musical signals. First, the algorithm detects the repetitions of each segment of fixed length in a piece using dynamic programming. Second, the algorithm summarizes this repetition information and infers the structure based on heuristic rules. The performance of the approach is demonstrated visually using figures for qualitative evaluation, and by two structural similarity measures for quantitative evaluation. Based on the structural analysis result, this paper also proposes a method for music thumbnailing. The preliminary results obtained using a corpus of Beatles’ songs show that automatic structural analysis and thumbnailing of music are possible.