Very rarely, if ever, a song is completely made by a single person. In bands, lyrics, chords and melodies come from different members, some times separately, some times during a brainstorming session. Both bands and solo artists ask for advice, second opinions, some feedback to get that spark, and more and more people get involved. Also, there’s the production chain: who owns the studio, who is behind the label?
It is a lot to consider, but don’t let it scare you. Listen to Millicent’s advice in regards of song share splits in this episode of Success Beyond The Score: