The UWM Libraries no longer maintains electronic reserves (with the exception of a list for the University Community Orchestra). Your faculty members will provide access to digital articles and links to streaming audio through your D2L/Canvas course module.
Physical Music Materials
Sound recordings and scores placed on reserve by faculty can be found at the Music Service Counter and may be checked out for use in this area.
Books about music might be at either the Music Service Counter (especially for music courses) or at the Media and Reserve Library Service Counter in the Lower Level of the West Wing.
Searching for the book in Search@UW will tell you where it is being held.