i want to map ardour tempo slider
to one of the controls on the midi keyboard so that i can adjust the tempo from the keyboard controller
is it possible to do?
No. Some MIDI control surfaces with extensive built-in support have tempo controls that work. But there is no way to bind the control of a generic MIDI controller to tempo. There probably ought to be.
thank you for the reply.
it would be wonderful to have such functionality. Please consider it a feature request.
Thank you for the wonderful software
The problem is with generic controller you don’t have enough values. 0-127 are too limited for tempo.
I may be limited. But it should be sufficient for some (including me) 
To limited for raw tempo, but might be useful as a control for changing the current or starting tempo +/-64.
It may works with some encoders but with a pots… So very limited scenario then complains about limited range, strange behavior. Not sure if it worth the effort…