Speaking of tone
Perhaps you see no connection, but it does happen for some. A whole host of notes already in place can work against your writing in a mental way as you start trying to create. It seems like it's cluttered and you're trying to write your ideas in the middle of what feels like a mess. I've read how some feel like they're fighting with the original song more than anything because it's already all there, getting in the way. Again, this doesn't happen to everyone, but it happens.
Either way, it was merely a suggestion. It's a good skill to further hone when you do get the time.