FM glass bell

A clear, ringing bell from one oscillator, using the FM-Lin Mutant at a non-whole-number Ratio.

Why it works

Linear FM uses one wave to wobble another wave’s frequency hundreds of times a second. When the two are tuned to a whole-number ratio you get a harmonic tone; at a ratio like 3.5 the new partials fall between harmonics, which our ears hear as metallic or bell-like.

Real bells are brightest at the strike and mellow as they ring. Routing ENV 1 to the Mutant’s Depth copies that: the FM amount, and so the brightness, falls as each note decays.

On the Hydrasynth Deluxe

1.
Press [INIT] twice to start from an initialized patch.
Manual p. 20
2.
Press [OSC 1] and set Wave to Sine with Control knob 2.
Manual p. 43–44
3.
Press [MUTANT 1], turn Control knob 1 to FM-Lin. Set Source to Sine, Ratio to 3.500, Depth to about 20 and Dry/Wet to 100%.
Manual p. 45–46
4.
Press [ENV 2]: Sustain 0, Decay about 3 s, Release about 2.5 s.
Manual p. 59
5.
Hold [ENV 1] and press [MUTANT 1]. The Mod Matrix opens at a free slot; choose Depth as the parameter and set a positive amount.
Manual p. 41, 92
6.
Press [ENV 1]: Attack 0, Decay about 1 s, Sustain 0. If the filter also sweeps, set Filter 1’s ENV 1 amount to 0.
Manual p. 54, 59

You should hear…

A bright ‘ting’ that melts into a pure, slightly hollow tone. Higher notes ring cleaner; low notes turn gong-like.

Variations

Ratio 1.000 with high Depth gives an electric-piano bark instead of a bell.
Route Velo On to Mutant 1 Depth so harder hits ring brighter.
On the hardware, try Feedback (0–150%) for a gritty edge.

Questions

Why does a non-integer Ratio sound like a bell?: FM creates sidebands at the carrier frequency plus and minus multiples of the modulator frequency. With a ratio like 3.5 those sidebands don’t line up with the harmonic series, producing the inharmonic partials typical of bells and metal.
Where is Ratio on the Hydrasynth?: On the MUTANT page in FM-Lin mode. It only appears when the FM Source is Sine or Triangle (manual p. 46).

Why it works

Real bells are brightest at the strike and mellow as they ring. Routing ENV 1 to the Mutant’s Depth copies that: the FM amount, and so the brightness, falls as each note decays.

On the Hydrasynth Deluxe

Press [INIT] twice to start from an initialized patch.

Manual p. 20

Press [OSC 1] and set Wave to Sine with Control knob 2.

Manual p. 43–44

Press [MUTANT 1], turn Control knob 1 to FM-Lin. Set Source to Sine, Ratio to 3.500, Depth to about 20 and Dry/Wet to 100%.

Manual p. 45–46

Press [ENV 2]: Sustain 0, Decay about 3 s, Release about 2.5 s.

Manual p. 59

Hold [ENV 1] and press [MUTANT 1]. The Mod Matrix opens at a free slot; choose Depth as the parameter and set a positive amount.

Manual p. 41, 92

Press [ENV 1]: Attack 0, Decay about 1 s, Sustain 0. If the filter also sweeps, set Filter 1’s ENV 1 amount to 0.

Manual p. 54, 59

Questions

Why does a non-integer Ratio sound like a bell?

FM creates sidebands at the carrier frequency plus and minus multiples of the modulator frequency. With a ratio like 3.5 those sidebands don’t line up with the harmonic series, producing the inharmonic partials typical of bells and metal.

Where is Ratio on the Hydrasynth?

On the MUTANT page in FM-Lin mode. It only appears when the FM Source is Sine or Triangle (manual p. 46).