One random variation I tried was to use the revered HCF4007UBE transistor array IC to build three individual CMOS inverters in series to create a ring oscillator of sort as shown in the below ...

In this article we presented a 20kHz-20MHz ring oscillator designed, fabricated and tested in a 40nm CMOS technology. For this kind of circuit, there is an obvious trade-off between output frequency ...

so has taken it down that path by producing a 74HC based ring modulator guitar pedal. In both circuits, a 74HC4046 phase-locked loop chip serves as an oscillator, driving a 74HC4051 analogue ...

CMOS ring voltage controlled oscillator with combined delay stages ... inverter versus supply voltage changing, so a combined schematic can be used to obtain better frequency stability.