A theoretical way of performing music.
Let's say you have an audience in the center of a very large clear area. Arrayed around them are a number of instruments. These instruments are only capable of playing notes of one pitch, although they are allowed rhythm and timbre. Each of these instruments is mounted on a platform capable of being moved very quickly. For an instrument to play different pitches, it must be moved either away from or towards the audience, due to the Doppler Effect. To keep the dynamics steady, the volume of the instruments will have to be increased as they recede.
Doppler music is practically impossible, but interesting. What is particularly interesting is that the music will vary dramatically based on where you are when you hear it. Entirely different tones, melodies, and chords could be heard by different listeners listening to the exact the same performance, but from different vantage points. | 
