I see that both Spotify and ASD have been discussed here but I don't see that they have come up together...
When I subscribed to Spotify, I was pleased and surprised to find that County's Clawhammer Banjo series was available. Totally unexpected and there are other worthwhile clawhammer and stringband materials as well.
I was equally pleased and surprised to discover, after getting around to upgrading to the current version of ASD on my iPhone, that Spotify was available as a Source.
I'm on the road working almost every week and travel with a banjo whenever practical. Being able to have a library of tunes to learn without ripping cds on the weekend and the tools to help me learn them, literally in my pocket, is a real pleasure. Give it a try if you have similar needs.
Cheers...TG
(Currently working on Wade Ward's version of June Apple trying to figure out the source of all the drive and richness I don't hear in my own playing. A fun but probably futile exercise even when working on the tune at close to a snails pace)