Just providing the schematic for the 4-step sequencer that I made, which is a basic design on the CD4017.
This schematic can be slightly improved by adding a 10k resistor between the OPAMP positive input and ground, as this will cause the potentiometers to become more logarithmic, thereby making it easier to tune in specific notes.
It can easily be expanded to 8 steps by moving the MR connection to Q8 and expanding it to Q4-Q7. Of course, even more steps are possible. Here is an example of the finished product with the 8 step expansion./
