The aim of this study was to compare the Query-by-Humming systems Midomi, Musicline and Tunebot regarding their retrieval effectiveness. The aim was to see if there were differences between the systems but also between the user groups common users, musicians and singers. Query-by-Humming system means that the user sings a tune that the system then use to find the right melody.To compare the systems and their users, queries where collected from the different user groups and replayed for the systems. Mean Reciprocal Rank and Friedman test was used to do the comparison.The results showed that the system did not achieve equivalent and that there were no difference between the user groups. The Mean Reciprocal Rank showed that the systems had very different retrieval effectiveness, where Midomi was the system with best result and Musicline with the lowest result. / Program: Bibliotekarie