3.5

89MainStage Instruments
• Edgy: Two- or four-pole analog-modeled filters. Four-pole variants provide a steeper
roll-off of frequencies beyond the cutoff.
• Gritty: Two-pole filters designed to saturate heavily at higher Resonance and Drive
settings.
• Rich: Two- or four-pole analog-modeled filters. Four-pole variants provide a steeper
roll-off of frequencies beyond the cutoff.
• Sharp: Two-pole analog-modeled filters.
• Smooth: Two- or multi-pole state-variable filters.
The three principal filter controls have standard functions for all filter types.
• Cutoff: Controls the filter cutoff frequency.
• Resonance: Controls the filter resonance or emphasis. Higher settings boost
frequencies in the immediate vicinity of the cutoff frequency.
• Drive: Allows the filter to be overdriven; the precise effect varies with each filter design.
Alchemy filter types: formant, notch, and peaking
A formant filter works like a bandpass filter with a potentially very narrow bandwidth. It is
designed to mimic a formant, or fixed resonance, such as those produced by the hollow
body of a guitar or by the shape of the vocal cavity (which is adjusted during speech to
produce different vowel sounds).
• Cutoff: Controls the resonant frequency of the formant.
• Amount: Controls the width of the band surrounding the resonant frequency. Low values
produce a narrow band, high values a wider one. Low resonance values may allow little
or no sound to pass through the filter.
A notch filter cuts a narrow band around a resonant frequency. The remainder of the signal
is affected minimally.
• Cutoff: Sets the frequency of the cut band.
• Amount: Controls the amount of attenuation.
A peaking filter boosts a narrow band around a resonant frequency. The remainder of the
signal is affected minimally.
• Cutoff: Sets the frequency of the boosted band.
• Gain: Controls the amount of boost. Higher values are generally the most effective.
• BW: Sets the bandwidth around the cutoff frequency.
Alchemy filter types: comb filters
A comb filter mixes the original signal with one or more copies of the signal which are
delayed by a very short time interval. At some frequencies this mixture causes phase
cancelations, while at other frequencies it causes reinforcements. The result is a spiky
frequency spectrum with multiple resonant peaks. Graphically, these peaks resemble the
teeth of a comb, which gives this filter type its name.
Alchemy offers three comb filter designs, each with its own character. The best choice is
very much a question of your preference and the type of sound you are trying to create.
That said, there are some distinguishing characteristics that may help guide you.