MUSE: A Musical Data Sonification Toolkit. Data sonification is the representation of data using sound. Last year we presented a flexible, interactive and portable data sonification toolkit called LISTEN, that allows mapping of data to several sound parameters such as pitch, volume, timbre and duration [20]. One of the potential drawbacks of LISTEN is that since the sounds generated are non-musical, they can be fatiguing when exploring large data sets over extended periods of time. A primary goal in the design of MUSE – a MUsical Sonification Environment – is to map scientific data to musical sounds. The challenge is to ensure that the data meanings are preserved and brought out by these mappings. MUSE provides flexible data mappings to musical sounds using parameters such as pitch (melody), rhythm, tempo, volume, timbre and harmony. MUSE is written in C++ for the SGI platform and works with the freely available sound specification software CSound developed at MIT. We have applied MUSE to map uncertainty in some scientific data sets to musical sounds.