Am I allowed to have a cd player or a cassette player in the bathroom, and when I take a bath or shower listen to Jewish music when I am in the water? Where is the Halachah written?

Shalom U'verachah, There are two different types of music. One is specifically Jewish, this includes music written for the different prayers or Nigunnim that were composed specifically for Jewish practice. The other type of music is music that is not Jewish in origin but was adapted with words from prayers or the Tanach to be sung. The first type would have more Kedusha than the second type. In practice it is forbidden to listen to music with words in a place that people are usually unclothed, the second type of music can be listened to, as long as one does not sing along the words to it or recall the words. I believe that it is inappropriate to listen to the first type of music even without words. Kol Tuv