It's actually about frequency, not necessarily the music.
There is a lot of conspiracies/discussions floating around about providing a 432Hz frequency, and how it makes living things behave.
Some think that the specific frequency resonates perfectly with nature, and helps plants with growth.
For me, I don't honestly know. However, if you listen to music specifically tuned to 432Hz, some people say that the music is more enjoyable (again, because of a more 'natural' frequency). I don't personally notice any difference, even after listening to the same song played at its normal frequency (440Hz) and the 432Hz remastered version. My wife claims she does, but I'd call her crazy if I didn't think she'd stop trimming for me at harvest time as retaliation.
It is an interesting theory though, that's for sure. More up my wife's alley (frequencies and how things resonate), but she's not home so I'm probably wrong about all of it