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User-friendly FM synthesizer with 4 operators, LFO, overdrive and a peculiar stereo effect

(19 Votes)
1.0 (Updated 9 years ago)
February 25, 2011
Reaktor 5 or lower


FM synthesis is a powerful sound design method. Alas, with most FM synthesizers you rather have to be a technical engineer to create new sounds. Consequently, many musicians feel discouraged and find themselves browsing through the presets only.
FUMB invites you to tweak knobs and explore the possibilities of frequency modulation simply by fumbling around.

The central panel of FUMB is organized in four rows. Each row corresponds to one sine wave oscillator and all possible modulations that can be applied to it. In the left part of each row, the oscillator's amplitude, key velocity, pitch and envelope are adjusted. In the central part, the oscillator is modulated by the other oscillators and by itself.

To the right of the FM matrix, the FM amount of each oscillator (NOT its pitch or its amplitude) is modulated by a central LFO which is adjusted by the controllers at the panel top. There, the LFO rate is adjusted and can be synced to the host tempo. The LFO envelope is a ramp envelope with two parameters, the delay time and the tempo of the fade-in. Note that the LFO envelope amplitude is overridden by the mod wheel. At the wheel's zero position, the LFO is completely controlled by the LFO envelope. By cranking up the mod wheel, you increase the LFO modulation amount.
Finally, the rightmost two columns of each oscillator's row set its panorama and output volume.

The total FM signal is fed into the effect section at the panel top next to the LFO settings. First, a peculiar stereo effect, the "LR Mangler (LRM)", is added that, roughly, sums and multiplies each voice with an inverted, phase delayed copy of itself. The result of the LR Mangler can be viewed in the phase correlation display. The parameters of the LR Mangler should be tweaked so that the displayed sound spreads into both dimensions of the display, giving a pleasant stereo image.
Lastly, the signal is fed into an overdrive unit, giving the sound a little warmth or, if cranked up, some good amount of dirt.

For those who are more familiar with frequency ratios instead of octaves and semitones, there is a converter tool in the panel's B view. Note that the "Fine" knob sets an absolute detuning, while the "Oct" and "Semi" knobs detune by an amount relative to pitch of the key pressed.

2011 by Kim Boström


Andrew Dauphinais
1 year ago
I'm a huge fan of this ensemble. It's probably the most user-friendly to-the-point fm synth in the user library and it sounds great.
Jeanne Corbeil
9 years ago
Thanx a lot!
Kim Joris Boström
9 years ago
Thanks for the feedback! "Usable" is a nice compliment (I take it), since this is exactly what I intended with this synth. You may want to check out the newer versions (2.0 and higher) which are in a different upload. (I somehow messed with the update procedure.) I leave the 1.0 version here, however, because it is a simplistic version without any filter stuff. Pure FM.
9 years ago
usable - fine!
William French
9 years ago
Interesting ensemble, and a nice idea for FM. thanks!
year zero
9 years ago
ahh..that first cup of coffee and a fresh reaktor ensemble. the perfect morning! thanks so much!!