Of the DS' major rhythm-action games, only Jam Sessions has made it to Europe with relatively little fuss - Ouendan took its sweet time, and the venerable Daigassou! Band Brothers never made it at all, despite rumours that it was in development for Western audiences as Jam With The Band. Shame, then, that Jam Sessions is ultimately the weakest of the DS' music games, although it's not without its uses. Where traditional rhythm-action games are essentially reflex tests, Jam Sessions is essentially a synthesiser instead, letting you make your own music instead of playing along to preset patterns like in Guitar Hero.
The game maps eight chords to the D-pad at a time, arranging them according to key, and then... well, that's it. You stroke up and down on the screen to play the chords however you like, and apply effects chains to mess around with the sound. Theoretically you can play anything you like, as long as it's all chords instead of crazy solos, and doesn't change key suddenly halfway through. It comes with a reasonable selection of song tabs to play along to - including German ones, hooray! - but really the idea is to experiment, imitate or compose on your own. It even comes with a trainer designed to help you recognise chords by ear.