Voltage Controlled Oscillator

I'm looking into how analogue synthesizers work and plan to build a couple of modules. The first module to build is a VCO, Voltage Controlled Oscillator. I found a simple one in The art of Electronics which i built on a copper plane, Jim Williams style.
 Schematics and images are shown below.

VCO on copper plane. A potentiometer is used as voltage source.

VCO schematic based on design from The Art of Electronics.

In The Art of Electronics, 1% resistors are used in the input stage of the first Op-Amp. I didn't have any such resistors at home, but it seems to work well with 5% resistors. Max frequency is about 50Hz, which means this design isn't very useful as instrument, but it gave me something basic to start with. Also, voltage output from sawtooth and square wave where quite different. The square wave comes from a comparator with the full supply rail as swing.

Sawtooth and square wave output from VCO.

In the junk room in my cellar, I found an old power amplifier with a lot of RCA jacks on the back, which I'll use to connect the different modules to each other. More on this topic later on.