Hi Peter
Found this on Wikipedia
The soft pedal (or una corda pedal) is one of the standard pedals on a piano, generally placed leftmost among the pedals. On a grand piano this pedal shifts the whole action including the keyboard slightly to the right, so that hammers which normally strike all three of the strings for a note strike only two of them. This softens the note and also modifies its tone quality. Tone quality is also affected by forcing the remaining two strings being struck to make contact with a part of the hammer felt which is not often hit (due to the whole action being shifted); this results in a duller sound, as opposed to the bright sound which is usually produced (due to the felt being hardened from regular use).
Digital pianos often additionally use this pedal to modify non-piano sounds such as the organ, guitar, or harmonica in ways appropriate to those instruments' playing techniques. Pitch bends, Leslie speaker speed, vibrato, and so forth can thus be controlled in real-time. The pedal is still sometimes called the soft pedal because of its position, but it may have another name like modulation pedal.
Maybe you could use the modulation control to simulate the sound you require .
Just a thought
Alan