■Japanese manual

STO is a compact analog oscillator that can produce various tones using wave shaping and FM.

You can't output for sawtooth or pulse waves, but you can create rich sounds by controlling the shape control with knobs and CVs, and also using FM. Depending on the shape, the sine wave gradually changes to a musical sound containing overtones, but the overtone component does not expand to the extent that the fundamental frequency becomes less noticeable. In addition, STO has the following unique functions, and offers a lot of options for moving the timbre.

Expo input
The Expo input is the second 2V / Oct input. If you insert another pitch CV here, two pitch CVs will be added, allowing you to shift the pitch. When oscillator sync is performed using the SYNC input, you can also create a strong tone change by changing the CV to the EXPO input without changing the pitch.

S-Gate
The waveform is reset the moment the sub-oscillator sound is produced by S-Gate. This allows you to sync only the sub oscillator with the oscillator's output by inserting the output of another oscillator into the S-Gate. 
 

The STO frequency is lowered and it is used like an LFO. LFO output from the sub oscillator that can be turned ON / OFF with S-Gate DPO It's input to the Exponential FM Input of, and it seems to produce a granular sound.