The only instruments that I can recall that had this facility were the Yamaha Organs, i.e. HS8, Hx's,. They had a 2 pedal arrangement, One for expression and another for tempo( and some other things, but I can't remember what). These were available from the mid.1980's. One way of doing it is to program in a chord sequence to leave your left hand free to slow the tempo manually with the tempo/data wheel or maybe you can operate the tempo wheel whilst you are playing.
peter b

[This message has been edited by peter.bentley@talk21.com (edited 01-19-2005).]

[This message has been edited by peter.bentley@talk21.com (edited 01-19-2005).]