VOLTIO is an accurate Manual Voltage Source. It is somewhere between a music tool and a piece of electronics lab gear.

It is Calibrated following the 1Volt/octave Standard to generate voltages equivalent to all the notes on
the 12-tone equal temperament scale, better known as the Chromatic Scale.
Additionally, The Precision Adder IN, lets you Offset the module’s OUT (or the module’s OUT to let you Offset
The IN depend on how you want to see it).

https://www.befaco.org/voltio/