There are many issues involved in getting the keyboard right. I can assure you that there is no "spongy" feel to my M4000 keyboard, nor could that term be used to describe the feel of the keyboards of the machines coming out of my shop.
In a message dated 1/15/2010 3:46:54 A.M. Eastern Standard Time, markpringnz@yahoo.com writes:
I can't remember who said it but playing a mellotron and certainly the M4000 I played can only be described as playing a sponge.