Two things to keep in mind with notes:
1V/Oct standard means that notes are placed with 0.0833… volt intervals in the ±5V range.
If the frequency of a given note is known, the same note an octave up will exist at double that frequency, and an octave down at half that frequency.
To get the frequency of a voltage note, use:
dsp::FREQ_C4*simd::pow(2,Voltage);
C4 is commonly represented as 0V in the 1V/Oct standard.