Make:

From the MAKE Flickr pool

Solipsistnation posted detailed info for the excellent MeggySeq project (we recently covered) -

MeggySeq has 8 patterns of 16 steps each. You can set each of those steps to play one of 8 WAV files on the waveshield. You can play the pattern back, stop it playing, and change the tempo. You can copy patterns from one slot to another. You can even save all 8 patterns from RAM to EEPROM so they won't be lost when you turn off the Meggy Jr.

You can loop patterns into longer compositions (up to 8 patterns long) and edit the patterns and pattern parameters (like tempo, loop length, and pattern length) without stopping playback.

You can edit one pattern while another is playing, and if you change patterns during playback, the first pattern will finish playing before jumping to the newly-selected pattern (or the next pattern in the loop if you've turned on looping).

In the Maker Shed:

Arduino WaveShield Kit

Meggy Jr. RGB Kit