MOTM

I haven't needed to do this, but for those of you without an oscilloscope,
you might consider this agonizing way of calibrating your sine shape.

Once you have the VCO built, try recording a short snippet of the sine
output into your computer's sound card and then look at it on screen in one
of a hundred different WAV editors. It's a pain to go back and forth like
that, compared to the real-time feedback of a 'scope, but you can probably
get really close by ear and then check it this way to satisfy yourself that
the sine looks good.

In fact, you may even be able to find a shareware program on the web that
lets you use your PC as a scope. I hear they exist. Be careful not to blow
up your sound card with high voltages, of course.