Yesterday I did a search on the internet to see if I could find a better way to brush up on bird songs (and learn new ones) before spring migration is in full swing than just listening to the compilations of bird songs that I have on itunes and on my iphone, and was rather excited to find a site called "Larkwire.com" which sells what seems to be a game based, match the bird to the song in various challenging ways... The approach seems to be progressive and increasingly challenging.. I've played it off and on for two days, and it seemed impossible at first.. I jumped to the "Pro" level package, though within that there are still beginner, intermediate, advanced.. and Master, I think. I've jumped to intermediate, and thought it does seem to be very challenging, I do think it is sharpening my ears a lot already. It does't give you just one version of a bird song, it throws in lots of variation that you don't get exposed to just listening to tapes.