Here is an example of linear FM using the Bogaudio VCO in VCV Rack. The “LINEAR” button on the VCO is selected and the large knob is set for 0V. The “V/OCT” input on the VCO is used (not FM).

When the 8VERT is set to scale to 10%, the SEQ-3 can be used to specify specific frequencies from 0Hz to 1000Hz. With this scaling , a SEQ-3 setting of “1.1” translates to 110Hz.

2 racks are included here – with and without the 8VERT.

Thanks to Deev Bennes on the VCV Rack Official User Group for pointing out the Bogaudio option.