If you cleared the data or cache for any of the apps, or even uninstalled and deleted an app that was attached to the music, the music could have gone with it.
However, first, you can try restarting the phone. It may just be a typical error that makes stuff not show after removing other things. Should that not help, then you will have to consider recovery software.
While there is no guaranty that you can get them back. Deleted does mean deleted. There are a few apps/programs out there that 'may' be able to help you recover the data.
A few of the programs you could try would be... DiskDigger, MobiSaver, Android-Recovery and Tenorshare. They are all data recovery apps/programs. There are many others out there, so check around and see...