What were some of the conditions, which prevented music in the middle ages from developing more rapidly?

Music was still underdeveloped due to various reasons. For example, there weren't that many instruments being used and music was mostly conducted vocally, with only a few types of instruments being used from time to time. Technological developments also obstructed this as Polyphony hadn't yet been discovered until later. Another thing was pressure from the church as there was a norm of what music should look like and be like and anyone who came up with the idea of making something differently was ostracized.