That's on my wish list, but I don't know how the app could reliably know that you have completed a song. It could use a song completion action, but you might move to the next song a few seconds early and that would be missed. It can't just check off every song you view because you might preview a few songs while deciding what to play next, or skip past a song after viewing it. It could have a minimum viewing time but that would be arbitrary and would still fail in some cases. Basically I don't want to add a function if I know it will fail sometimes.