Well there's not much to explain here.
The system would be installed to provide "live" music to large buildings which already have extensive plumbing and echoing, cavernous interiors.
The pipes would probably have to be adapted a bit to produce varying sounds. Also the system would have to be
calibrated so that nobody gets wastewater shot in their face. Perhaps it might have to adapt to the usage level of the pipes.
The music itself would be programmed into a player piano sort of contraption.
If mild enough, the bubbling effects of urinals, toilets, sinks, etc, could add to the entertainment factor.