There is an awesome band I know for string music (violin/cello) called Vitamin String Quartet They take modern songs, everything from pop, rock, indie, and slightly older blues, classic rock, techno-y hip hop, etc. music and play it as a cover song entirely on string instruments (with no vocals at all). They have I think about 200 albums on their iTunes store, you are likely to find if not an album on an artist you've liked now or in the past, at least dozens on artist's you've known that sound beautiful on cello/violin

Vitamin String Quartet's YouTube Channel!

Look them up on iTunes and download an album! My personal favorite album by them... hmm... There are SO many albums on their iTunes site that it's intimidating! I know I get overwhelmed when I look through too many albums on their site, and I hate recommending exact albums by them because they have sooo many but here I go... Don't just buy these cause I said them (look for an artist you've known by typing them into a search box first and always preview! It's a lot of fun finding a string cover album on a favorite band!)

I enjoy both of their Emo Anti-Valentines Day Collections, all of their Wedding Collections (especially the 'Modern Wedding Collection') and I like their 'Vitamin String Quartet Preforms Muse' as a more recent addition to their music repertory but most of all I recommend typing in an artist's name that you know such as "so-and-so's-singers-name-that-I-like" and looking if they have anything by them on the iTunes search for their iTunes store. They have a couple hundred records I think? It's huge, so look for something you know and preview it before you download cause there is tons! (if you like it... cause it is awesome modern cello/string instruments!)

Oh and... I looked they are also on many other online retailers as well, so check your other internet download websites or album sellers online (though I doubt if you'd find them in an actual store, just other places online).