Possible Clues:

• Roman god of song on new record
• Writer's come up with a melody for god
• Poseidon's counterpart
• Trident bearer
• Writer comes up with a melody for a god
• Write about air that circulates in space
• Write up a song of the sea for him
• Roman god backing exercise in northern air
• God, planet
• Will he write up the music for 8 down? (7)