There should be a multisample called A.Piano-M1 that can be used to create an M1 Piano Program. This is the basis for the Korg M1 Piano sound and is #0009 in the Multisample ROM. From the Osc page, it's possible to select 8' or 16'.
Thanks for this, thats the sound I'm looking for! Do you also know how to make it velocity sensitive? The sound I have is raw with no velocity variation.
Find a Piano program that uses the HD-1 Engine, and write it to a new program location and rename it M1 Piano. Then edit the program, and change the multisamples so that it only calls up that one M1Piano multisample on OSC1. Change the velocity window so that it responds to 0-127. Done.
There's quite a bit going on in the original M1 piano sound. Several things need to be done with the basic sound contained in the Multisample to make it sound close to the original M1 piano:
Amp/EQ tab - Amp 1 Mod - adjust Velocity Intensity to some positive number to get the necessary velocity sensitivity.
Amp/EQ tab - Amp 1 EG - to adjust volume over time (basically ADSR on steroids). The Multisample won't decay until changes are made to these settings.
Then there are the Stereo Delay and Ensemble Hall effects chained.
The original M1 piano has a small amount of pitch bend, and also a bit of low pass cut-off with ADSR parameters controlling the effect.