Have you visited this site yet? If you are a musician you should have a look. They have sheet music of all sorts, all by Scottish composers and songwriters, both ancient and contemporary. There's lots of traditional Scottish music, but there's so much more besides - Jazz, Classical, Gaelic... the list goes on.
You can see the music, listen to it, buy it and download it straight to your printer. It's very easy. Most pages are only 50 pence. Some of the sheet music is FREE too.
It's a great resource for fiddlers particularly, but also stocks music for piano, clarsach, guitar, guitar quartet, string quartet, gaelic songs, trombone.... you name it. And the wealth of Scottish composition talent it shows is vast!
If you are a Scottish composer or songwriter yourself, you should get in touch with them and get your music on their site. You could earn yourself some extra cash!