I did an experiment one evening a while back. I took a public domain song's lyrics, and I wrote music for it and recorded it. THEN... I listened to the original writer's music. It was fun to see what similarities and differences came from the same lyrics. The song is an old hymn and you can hear my rough version below before reading on.
Hear My Humble Cry (Blake Flannery version of Pass Me Not)
Now, listen to the original version of Pass Me Not, O Gentle Savior Here. I think my version sounds more dark and desperate, which is how I interpreted the lyrics, but there are some similarities. On the "Savior, savior... " melody and timing match closely and sound like a crying out.
I also found out that the length of words and lines in lyrics, as well as the content of the lyrics, steers the direction music will go. Notice, I didn't write music that was extremely different, but it wasn't the same either. The content of lyrics only steers the musical ship in a direction. The exact place that ship lands could be different depending on the day you are writing music, but you'll still end up in the same country. I think I subconsciously write music to match the lyrical content, and the length of lines determines cadence, timing, rhythm, etc.
Musical influences are different for everyone. And the instrument you play is probably your biggest musical influence. That instrument has qualities that limit your creativity to be focused in a certain direction. I used a guitar instead of a piano, a
Personalities can never be the exact same in any two humans, and I believe songwriters write songs as unique as their personalities. If one person writes the lyrics and another writes the music, you are essentially blending personality and experience of both writers. This can create some interesting mixtures. Collaboration is a beautiful thing.