usually there are fiddles, banjos, mandolins and guitars in bluegrass bands. a cello? you wouldn't believe how nice it is when they add a cello to it.
violins are normally associated with classical or light and sentimental music. mostly it's for serious stuff. but country music, especially bluegrass, has made violins, or fiddles, express feelings and emotions in drastically different styles. a fiddle is a very versatile instrument.
there are sub-groups within bluegrass. enthusiasts may be crazy about some but not all of them, just like in any other genre of music.
how's it sound like anyway? well, find out for yourself. you may not find it so appealing, or you may fall in love with it: