Min max
Use the expression min(max(v, 0.5), 1.25) or its dual max(0.5, min(v, 1.25)) where v is the driver variable (sound curve value)
>>> v = 0.05
>>> min(max(v, 0.5), 1.25)
0.5
>>> v = 3
>>> min(max(v, 0.5), 1.25)
1.25
>>> v = 1.1
>>> min(max(v, 0.5), 1.25)
1.1
If you wish to double the variable v simply replace v with 2 * v in expression.
I would recommend you normalize the values in some way What's the range of values on a sound-baked f-curve?
Related
How to set driver distance max and min influence?
Full story post at
https://blender.stackexchange.com/questions/133285/add-min-and-max-values-to-driver-expression
