Were musical instruments alowed in the temple holy and holy of holys? There appear to be examples of musical instruments on the temple grounds but is there any law allowing musical instruments in the temple sanctuary, the holy  and the  Holy of holys?
Except for maintenance, nobody was allowed in the Holy of Holies but the high priest on Yom Kippur and music making was not part of the service.

I Chronicles 25 talks about the musicians who worked in the Temple and their instruments.
http://www.chabad.org/library/bible_cdo/aid/16545