here's another demo . i just finished this vco from Mordent Design which is actually Electronotes VCO from issue #75 i believe ,it's a thru zero VCO ,the newer Electronotes Zero VCO might behave smoother when crossing zero , but anyway i like this older version a lot too ,here's a short recording of it making vowel like sounds ,this part might not be thru zero i didn't checked on scope .