I liked this, it had charm and grace. It was written well enough so I could visualize everything.
A few things with the story flow felt off. Renner bonded with Gail extremely quickly. In one scene he's kidnapped her, the next he has her in her home, the next she's had the accident and he'll do anything, even betray everything he believes in to save her. I didn't buy that, you hadn't laid the groundwork for me to accept this was real.
Renner flips to the dark side quite quickly. The 'only music can save her' option is presented and accepted very early on. My first thought was, why not just try singing? Anyone can sing, even badly. Playing a guitar takes weeks of practice and requires instruction. This element felt forced just so you could bring Cecily into the story.
The ending, although charming, was telegraphed and again didn't seem believable. I think this would be a much more realistic story if music didn't save his daughter but it saved him. In his desperation to save her, he tries forbidden arts and, although it doesn't bring her out of the coma, he learns an important lesson; that type of thing.
To summarize, this feels rushed and that gives the script a forced element that snaps the suspension of disbelief. But it's a good start and there's potential here so keep at it.
Maybe try starting the story later one once she's in the coma and use a few brief flashbacks to fill us in on the backstory?
I hope my notes help.