Have to be sent separately

If other people wrote the music, do these works have to be sent separately, even though someone else is the creator/owner of the lyrics?

No, but credit should be given to the authors of the music on the form that's submitted. A space is provided for this on the form (PA). The last song I registered had a small section of cello music that was created by another person. The lyrics and basic melody, guitar parts, etc. were created by myself and my husband. We used one form for everything.