Fair use allows limited use of copyrighted material without permission for purposes such as commentary, criticism, news reporting, research, teaching, and scholarship. It is determined by a four factor balancing test. Selected guidelines provide specifics on fair use for classrooms, off-air recording, and music. For classrooms, a single copy can be made of portions of copyrighted works for teaching. Off-air guidelines allow recording TV broadcasts for up to 45 days for instructional uses. Music guidelines permit emergency copying to replace unavailable copies and limited student performances of excerpts. Proper attribution and limits on extent of copying and re-use must be followed.