It`s possible to do it if the file isn`t protected.
See, there are some uneditable .hfs files. (If you edit them- game won`t work)
If the .hfs is protected than it won`t work, if it isn`t - it`ll work.
And I think you gotta make sure the song you change it to is rendered the same way the original wav file is (kbps and rate o: )