This topic dates back to the 70s. I think the only way you can get info would be to google it.

It's not so much the music but the vibrations from the music that benefits the plants. You can get even better results from brushing the seedlings lightly with paper, turning a fan on them for a gentle breeze or even just shaking them. It's referred to as thigmomorphogenesis.

"Thigmomorphogenesis is the response by plants to mechanical sensation (touch) by altering their growth patterns. In the wild, these patterns can be evinced by wind, raindrops, and rubbing by passing animals. Example being the Venus flytrap.

M.J. Jaffe discovered in the 1970s that regular rubbing of bending of stems inhibits their elongation and stimulates their radial expansion, resulting in shorter, stockier plants.

Growth responses are caused by changes in gene expression. This is likely related to the calcium-binding protein calmodulin, suggesting Ca2+ involvement in mediating growth responses."