[martin@localhost test]# ls -slR
.:
total 4
4 drwxr-xr-x  3 root root 4096 Nov  6 11:16 1
0 -rw-r--r--  1 root root    0 Nov  6 11:16 a.mp3

./1:
total 4
4 drwxr-xr-x  3 root root 4096 Nov  6 11:16 2
0 -rw-r--r--  1 root root    0 Nov  6 11:16 b.mp3

./1/2:
total 4
4 drwxr-xr-x  3 root root 4096 Nov  6 11:16 3
0 -rw-r--r--  1 root root    0 Nov  6 11:16 c.mp3

./1/2/3:
total 4
4 drwxr-xr-x  2 root root 4096 Nov  6 11:16 4
0 -rw-r--r--  1 root root    0 Nov  6 11:16 d.mp3

./1/2/3/4:
total 0
0 -rw-r--r--  1 root root 0 Nov  6 11:16 g.mp3

[martin@localhost test]# find . -maxdepth 3 -iname '*.mp3'
./a.mp3
./1/2/c.mp3
./1/b.mp3