Next step - next jig (again printed from PLA):

This jig helped soldering the components of the tone generators a lot. After some practice I managed to solder between 3 and 4 in an hour. Compare this to the prototype!

And of course the circuit:

The CNY70 and the 1k resistor at the output were added later. I mostly connected LEDs of two CNY70s in series with 33R to my +5V supply voltage. If this was not possible, I used 68R.

The capacitor at the output was added much later. After I had soldered everything together the sound was much noisier than before with individual tone generators. So I added the capacitors. However, since everything was already soldered together this was not easy. Some are therefore really askew. But I was happy when I had managed to solder them without damaging some other parts.