This isn’t a tutorial as much as a photo-diary of the steps I followed to create this painting. It’s really very simple, so I’m tagging it as beginner.
Honestly, the most difficult part is getting the violin symmetrical! If that’s something you struggle with, you can always try to find a stencil or print out a violin to trace (though I don’t know how well you’ll be able to trace through watercolour paper). If you’re not feeling the violin, I bet this kind of thing will also work well with flowers, skylines or whatever else blows back your hair.