When it's Bluegrass it's Fiddle Racerback Tank - Women's 

Only available through Bluescentric, this bluegrass racerback tank top is available in comfortable, relaxed-fit women's sizes up to 2XL. The material is premium fabric-laundered 4.2oz triblend 50/25/25 polyester/combed ringspun cotton/rayon with a racer back. 

It's not the instrument, bluegrass fiddling is mostly done on a violin, it's the way they play it! 

Once uttered by the great Texan Hank Hill, true fans understand that when you're playing bluegrass... you call it fiddle. 

This design was specially made for fans of bluegrass & fiddlers. It reads "When It's Bluegrass, it's Fiddle", with f-stop style swashes and a violin design.