Attach photo of my Progrock2 "What IF" board. The Edge connector was cut from a larger 32 pin connector. Dip switches are used for "Bank" selection and allow the board to output on  8  frequencies.  The  output Photo Jack can be moved to any of the three CLK outputs. Power is a 9V battery.
Blank PC soldering pads allow for playing   "What IF".  My next "What IF" board will have an additional dip switch for CLK output selection and increase the board output capability to 24 programmed frequencies.  TIP: The outputs (CLK) are not buffered  -  you have to add a capacitor in series. If the board looks a little ruff and like it was assembled late on a Saturday night in 45 minutes - you might be right.
Z