Rugged Circuits just released this: http://www.ruggedcircuits.com/html/megaram.html
The MegaRAM shield adds 128 kilobytes of external RAM to your Arduino Mega or Mega2560. Fast zero-wait-state access lets you process or buffer large, fast incoming data streams, like images or audio. Or use it for storage or buffering writes to slower storage like SD cards or FLASH memory.
That would be great for audio based projects.
Wk
Looks like a breakthrough type product, I just put my order in for one.
Lefty
If I had a 1280/2560 based Arduino, I would definitely buy this.
But I've got 2 duemilanoves, and I don't plan on getting another arduino in the near future.
I guess I'll have to settle with generative drum sounds for my WIP sequencer/synth, like I already have: mah 64 step sequencer
Huh, coincidentally ruggedcircuits was the first guy to comment on that project when I posted it in exhibition in the old forum.
And your point is?
In any event, I saw your video, but those are just chip sounds, we are talking mostly about PCM sound processing, like the BeatVox, which runs on a regular Arduino 2009. 
And also the 8 voice synth project:
Wk
I was just saying that since there are 2 methods of synthesizing drum sounds, sample based and generative, I prefer generative methods, since the duemilanove doesn't have the memory for more than a few short samples.
My work-in-progress synth sequencer will sound a lot better than the video I had linked to. In that video, all the drum sounds were only 1 bit audio, recorded thru the built in mike in my computer.
(and it was a random pointless note about ruggedcircuits happening to comment first on the topic for the old synth.)
Wow very cool but most importantly IMO, it gives you specific examples for how to enable the XMEM feature on those ATmega processors that support it, and how to use it.