Hi David,
for $i in //* return rename node $i as lower-case(name($i))
for $i in collection("OpenSongSearch") return rename node $i as lower-case(name($i))
The following query should do what you need (collection() does work here, too):
for $i in db:open("OpenSongSearch")//* return rename node $i as lower-case(name($i)), db:optimize("OpenSongSearch")
The attached optimize call will update your index structures.
Hope this helps, Christian