The K5 is a 5 sine oscillator in a 8-pin DIP.
1 analog pitch input CV for the fundamental. 1v/oct.
4 analog levels CV for level of the 4 overtones.
This is the synth that requires no filter for shaping. because you can modulate the harmonic content of the fundamental frequency.
$15 including shipping.
There is also a LFO version of the chip, the KL5 Harmonic LFO.
Same function but LFO-range of the fundamental frequency.