Well I've been having my computer alarm play some Theta monural beats and frequencies at 5:00 AM. Usually these types of sounds do not come through in the dream (although can help you attain lucidity due to entrainment on the brain). In the dream I was in some sort of music museum and I remember the musuem was a tribute to the band RUSH (early progressive rock). Anyway in this store/musuem they had all kinds of instruments you could play. I heard the low vibrations (in the real world) from the THETA frequencies played by my computer..but in the dream they came across different. They were very vibrating tones in the dream, and while I was walking through the music musuem I heard it. I said "someone is playing a very wierd instrument!"