Bought a single from iTunes? Want to buy the rest of the album? Well, you always could, just by buying all the other tracks one after the other, but Apple has finally added a button to do it with a single click.

Actually, this new Complete My Album is more useful than it sounds, given the number of albums that contain long tracks only available if you buy the entire collection in one go - something you wouldn't want to do if you'd acquired, say, three of the songs singly.

The CMA feature works like a full purchase, but then credits you back the 99c/79p you'd already spent on individual tracks, as if you'd never bought them on their own.

There's also a sales scheme here. In an era of declining album sales - driven by a desire on the part of music buyers to pick the songs they want and not pay for the ones they don't - CMA is a mechanism that may help encourage folk to buy albums again. Well, we'll see...