For a local business, just starting a page and asking your friends and colleagues to share and like it would probably be more effective than paying for ad space.
offer periodic sales or specials via the page, and promote the page IRL via business cards and flyers as well.
Setup an Instragram, too. Post pictures of products, or do facebook contests. "Win a $100 gift card when you tag a photo of your instrument with #nicetiesmusicstore!"
Just a suggestion though I'm no exert. Most sites that claim to teach online marketing, SEO
, etc are all scams in my experience.