PathToGUID doesn't work on iOS64.

Unity
4

You can also try modifying fmod_studio.cs so that System.lookupID becomes

    public RESULT lookupID(string path, out Guid guid)
    {
        byte[] rawguid = new byte[16];
        byte[] utf8 = Encoding.UTF8.GetBytes(path + Char.MinValue);
        GCHandle pinnedArray = GCHandle.Alloc(utf8, GCHandleType.Pinned);
        IntPtr pointer = pinnedArray.AddrOfPinnedObject();
        RESULT result =  FMOD_Studio_System_LookupID(rawPtr, pointer, rawguid);
        pinnedArray.Free();
        guid = new Guid(rawguid);
        return result;
    }

and the declaration for System.FMOD_Studio_System_LookupID becomes

    private static extern RESULT FMOD_Studio_System_LookupID(IntPtr studiosystem, IntPtr path, [Out] byte[] guid);