You can use `sort -R` to reorder the file list into "random" order. The command could be the following:
find ~/Music -type f | sort -R | xargs -I + play +
Here `find ~/Music -type f` results in a list of of all files in the `Music` subtree, recursively. The resulting pathname list is then "sorted" into a random order by `sort -R`, and passed as arguments to successive `play` invocations with some few/many pathnames at a time. Note the use of `+` as "replace string", to invoke individual `play` for each music file.
(Edit: as per Warren's comment below, I've now removed the useless but harmless single quotes for the second `+`.)