Query-by-tapping systems are content-based music retrieval systems that allow users to tap or clap in a microphone the rhythmic pattern of the melody requested. In this paper, a new query-by-tapping system is described. This system is based on adaptations of alignment algorithms successfully applied for melodic similarity estimation. A similarity score is computed according to the cost of the elementary operations necessary to transform the query into the musical piece tested. A new method for extracting the rhythmic pattern from audio signals is also presented. This method is based on the analysis of the variations of the kurtosis computed from the audio samples. Experiments performed on the MIREX 2008 database show that the alignment technique proposed performs better than the participating algorithms. They also confirm the interest of the kurtosis-based analysis method in the case of noisy percussive queries.