Types of Fre­quency Mod­u­la­tion

Future Music - - REVIEWS -

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.

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