User Manual

APPENDIX A: THE DIGITONE KEYS FM SYNTHESIS
87
In some instances, an operator can be both carrier and modulator. This means that it outputs its result as
a tone while also using it to modulate another operator. We have divided the operators into three groups:
C, A, and B (B1 and B2) to lessen the complexity and make the Digitone Keys easier to use. Since group B
consist of two operators, the parameter controls for B are macro mapped to both operators.
A.3 ALGORITHMS
An algorithm is a set routing, or combination, of the operators. Routing the modulation in dierent ways
gives you several dierent methods of applying modulation and naturally dierent results.
CarrierEnvelopeModulator
Feedback
Feedback
Modulator
Envelope output
Carrier
Direct output
Output
Algorithm
Modulation
Level
Pictured above is a 2 operator algorithm, which is FM synthesis in its most basic form. The Digitone Keys
has four operators available which can be routed in many dierent ways. Dierent algorithms dramatically
changes the characteristics of the output - for example stacking four operators can lead to very complex
timbres.
The Digitone Keys has eight dierent algorithms where the four operators are routed in dierent ways. For
more information, please see “11.3.1 ALGO” on page 46. Each algorithm has two carrier outputs (X and
Y) that come from two dierent operators depending on what algorithm you chose. It is possible to use the
MIX parameter to mix between these outputs so that you can cross-fade between two separate timbres.
For more information, please see “11.3.8 MIX” on page 46.
1 2 3 4
5 6 7 8
The lines going to X and Y indicate the output from a carrier. There are two dierent ways a carrier output
is sent to the X/Y outputs: 1. Its amplitude is unaected by the operator envelope (dotted line). 2. Its ampli-
tude is aected by the operator envelope (filled line). The sound from the X/Y outputs is then routed via the
overdrive to the filters.
A.4 FM RATIOS
Frequency modulation is applied in multipliers of the principal frequency to retain the sounds tonality. These
multipliers are known as ratios. Each operator group’s ratio is a multiplier of the input pitch (note value). The
higher the ratio, the higher the pitch frequency. For example, when applying modulation with a ratio of 1:2
(carrier:modulator), the carrier output resembles a square wave. A ratio of 1:1 sounds like a sawtooth, and
odd numbers can be used for various metallic or other “natural” sounds. In Digitone Keys, the FM ratios for
the dierent operator groups works like this: