Types of Frequency Modulation
The Cš-L can switch between two types of frequency modulation: linear and exponential. Linear FM shifts the carrier pitch by a number of hertz rather than semitones, enabling the VCO to stay in tune unless the modulation depth is pushed really hard. This makes it more suitable for melodic lines. Exponential FM works the same way as the 1v/oct scale, it creates more aggressive sounds and causes the VCO to go out of tune when you change the modulation depth so it’s more suitable for atonal noises or percussion. There is a third type called linear through-zero FM which allows the VCO to stay in tune regardless of the modulation depth by reversing the waveform when it hits 0Hz. This is how digital FM works and it has now been implemented in a few analogue oscillators as well. Unfortunately the Cš-L does not feature through-zero FM.