I have exactly the same code as in here https://forum.phalcon.io/discussion/598/insert-new-data-with-manytomany-relationship#C2482 and it does not save related songs at all. This code produces an error:
songs_id is required
It seems some guys here at forum have the same behavior.
phalcon 1.2.1, linux mint x86_64, kernel 3.5.0-17