Czechoslovakia issued this stamp (Scott #2513) 5/11/1984 for "music year." It was part of a small set of two, the other featuring a keyboard, horn and violin,
Interestingly, 1985 was celebrated as a "music year" by the European Union, with many stamps issued by many different countries. 1985 was an anniversary year for the deaths of both Bach and Handel; several of the 1985 music year stamps feature those two composers. So perhaps this stamp was intended to be part of that series, though Czechoslovakia was not then part of the Union, just a few months early.
I cannot find information on the faced pipes in the stamp image. The words make reference to a "Czech museum," but I don't know which one.