I have a large collection of music living in iTunes and I want to make some of this music available on my Nexus S phone. I am comfortable buying music through iTunes, but iTunes won't talk to my phone. I would like something like iTunes for managing my music library that lets me legally purchase new music directly from a reputable online music store (e.g., Amazon or similar). I also like the sorting, searching, and playlist management in iTunes and hope that there is a desktop application like this to manage my music. I don't want to have to enter my payment details each time I want to buy a song and I want the desktop app to sync with my phone. Can anyone recommend such a tool? I've heard of doubletwist -- is that such a tool or does it just rip your files from iTunes?