It seems to me like music has a clear value for survival. Music is a type of cultural transmission (memory technique), and humans do sexually select for musical ability (ask a musician).[1] Groups that sexually selected for the ability to transmit oral knowledge through generations (via memorization, including things like meter, rhythms, melody, and rhyming) probably had a greater chance of survival. Before writing, people stored their cultures' encyclopedias in their minds, which often involved music in some way.[2] Cultures also organize around music, people follow the ideas of musicians, etc. Napoleon made some interesting comments about the active use of music in leadership and group behavior.[3] A prehistoric human with an ability to organize groups through music probably had a higher survival/reproduction rate in general, or at least benefited the group through organizational techniques.

[1] http://journals.sagepub.com/doi/abs/10.1177/0305735613482025

[2] https://www.allenandunwin.com/browse/books/general-books/pop...

[3] "Of all the fine arts, music is the one which has the most influence on the emotions, and it is this influence which the legislator must encourage most warmly. A piece of "moral" music, one by the hand of a master, cannot fail to touch the heart and has much more influence than a good, "moral" piece of writing, which moves the mind but has no effect on our behaviour."