OSX : tag and put the covers for MP3 automatically
Anyone who has used Windows in the past, or anyone who is accustomed to OSX but is not satisfied (go, I know you are not 😛 ) the simple RICERCA ARTWORK di iTunes (which among other things requires you to enter your iTunes account or, in case of creation, between the data also requires that of credit card, a bit useless if you do not buy songs from Apple Store, true?), especially if the owner of an iPod, will have had the need to properly tag the songs, to improve visualization of the songs on the iPod is, che su iTunes, than on any other software (About, if you need to convert mp3 and tag them automatically under OSX, read this article).
Undoubtedly one of the best programs in Windows for this kind of situation is tagrunner, shown here in full screenshot.
Though a fee, is by far the most convenient program to tag, add covers and lyrics, all automatically, and can subsequently refine the results before saving.
Regarding OSX, until a few years ago there was not much of a girlfriend available, I remember an application that did its job by using Musicbrainz, but it was in java and then an unheard HEAVINESS.
Finally, the eye fell on an application called MPFreaker that, in the same way Tagrunner, by entering any number of mp3, compiles correctly using Amazon for covers, and Musicbrainz and texts for the tag, le tag id3.
First:
after:
Unfortunately, this also as its analogue for Windows is not freeware, but you can download a trial version at this address.

Interface mpfreaker
On this date, and after years, I could not find a better program, if you have any suggestions on similar programs, do not hesitate to write.