I just sent Simon an email message with the location of the Ketron X4 MP3 piano demos. He will make these demos available in his site. Following his remarks, I rerecorded the midis with a stronger signal, and a constant 128 Kbps.

I also added the Walk midis, thanks to the work of Andrea (Dreamer), that removed all the aftertouch midi messages from the files (the Ketrons apparently don't like them!).

The MP3s are here: http://vega.estig.ipb.pt/piano_comparison/

-- José.