No, it’s a summing node, and I shouldn’t post when I’m low on caffeine 
You need to measure the voltage on the other side of the 100k resistors to see the voltages going into the node.
So I’d suggest:
- With power off, make sure that you have 100k resistance from the centre note trimmer output to pin 15. Check the same for fine tune, the octave selector, and CV in.
- Power on, and measure the voltages on the centre note trimmer and the others, on the trimmer/knob side of the 100k.
- Pin 15 will see the sum of these voltages (but your multimeter will read near zero on the pin itself, since it’s a summing node and the input opamp pulls it down to a virtual ground).
- Sweep the centre note trimmer across the range, check that the voltage at the trimmer changes, and listen for an audible tone.
Alternatively, use Jos suggestion with a separate voltage into CV in, after verifying that you have 100k continuity to pin 15. Pin 15 will see the sum of the ones you measured in step 2 and your additional CV.