I also want to know about it. I want to change the tempo manually. I have used MIDI-MAP on the top-left of Ableton screen and assigned to a rotary knob of my midi controller. It works but the changes are very erratic as the range is 20-999. .... I swear one time when I tried to assign, it asked me the lowest and the highest tempos. But I cannot get that again. I don't know how to change those CC values.
Amazing tip thnxs... But What if I need a higher tempo in the project than the sum of the initial tempo + 127? For example if my initial tempo is 40 bpm and my final tempo is 190 bpm 
"First, you need to reprogram your MIDI controller to have two buttons send the same MIDI CC message. One button will decrease the tempo by sending the value 65, and another one will increase it by sending 1. The exact variation in the tempo that these buttons will send varies on the tempo range (visible in the MIDI mapping table), and the values that you send. Sending 65/1 will alter the tempo in the smallest possible amount. To alter the tempo with the largest possible amount, have your controller send 127/64 instead."
Whoa, crucial!
incredibly simple and logical solution - just what I was looking for. THANK YOU
Man, what a golden tip. Very smart. Thank you so much!
THANK YOU FOR THIS! This has been driving me nuts, such an easy fix
Always thought that decimals for the master tempo were unnecessary
I also want to know about it. I want to change the tempo manually. I have used MIDI-MAP on the top-left of Ableton screen and assigned to a rotary knob of my midi controller. It works but the changes are very erratic as the range is 20-999. .... I swear one time when I tried to assign, it asked me the lowest and the highest tempos. But I cannot get that again. I don't know how to change those CC values.
BTW I am using m-audio midi controller keyboard and am using one of the rotary knobs
thank you for being the man
This has been driving me nutz as well, thx
Great tip thanks
Thanks a ton for this tutorial :)
THANK YOU!!!!!!
I really needed this much appreciated
this worked. Thank you!
So how do you change CC values. I am using oxygen 49 and I am able to MIDI-MAP but do not see place to change the values
This is clever!
thx!
Thank you!
So smart !!
Amazing tip thnxs... But What if I need a higher tempo in the project than the sum of the initial tempo + 127? For example if my initial tempo is 40 bpm and my final tempo is 190 bpm

"First, you need to reprogram your MIDI controller to have two buttons send the same MIDI CC message. One button will decrease the tempo by sending the value 65, and another one will increase it by sending 1. The exact variation in the tempo that these buttons will send varies on the tempo range (visible in the MIDI mapping table), and the values that you send. Sending 65/1 will alter the tempo in the smallest possible amount. To alter the tempo with the largest possible amount, have your controller send 127/64 instead."
lol, nice. would have never thought of this
But I don't get the field where to punch in the value as explained.
1:03 Nice
🤯