My opinion: Most of the newer e-ink kindles don't have sound. Probably not worth the official azw route. If you find an open-source front end to spotify, go for it - it would be a great leaning experience, but in the end, it is still not really a great tablet. It IS a great ereader, and I did make compile pianobar (front end for pandora) for my linux touch. Great fun doing the compile and stuff, so if it's for your own pleasure, do what YOU want! I doubt there is a market for it...
Have fun!
hm a command line client would be pretty easy:
http://mitchfournier.com/2013/03/26/...-raspberry-pi/
post 31 has directions for pianobar, SHOULD be simple to convert?
https://www.mobileread.com/forums/sho...light=pianobar