You will not lose your music by clearing the cache partition. This process clears background files and processes that may become corrupt over time. It is always recommended to keep your phone backed up to prevent the loss of data. However, as long as you aren't factory resetting or clearing data, you should be fine.
Hey there. As @SamsungRei stated, no you will not lose any data or files. Clearing the cache simply removes the stored copy of data. Cache on our phones is a software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere.