Electroplankton is now out in the US but remember that the DS is region free for UK DS Owners:
In Electroplankton, art and music collide to create a wildly fresh interactive audio experience. In this title, featuring the striking visual style of Japanese artist Toshio Iwai, you can poke, rub, and draw on the touch screen to stimulate odd aquatic creatures and create your own music. Each of the 10 different types of Electroplankton features a completely different sound style, ranging from haunting melodies to head-nodding beats to funky Mario theme remixes. One even acts as a sampler, allowing you to record up to four sounds and layer them over drum loops. Create new songs and experiences every time you play!