Voltage Controlled Filter and Filter Envelope Generator
Memorymode 2’s Voltage Controlled Filter is where the raw power of its three oscillators is shaped into something musical. The oscillators provide the harmonic material, but the filter determines whether that material becomes a warm pad, a sharply articulated bass, a brassy sweep, a hollow resonant whistle, or something else altogether.
The filter is based on the classic transistor-ladder lowpass design associated with the original Memorymoog. Lowering Cutoff progressively removes high-frequency content, producing a darker, rounder sound. Increasing Emphasis reinforces frequencies around the cutoff point, adding definition, bite, and eventually self-oscillation.
Memorymode 2 features substantially enhanced analog modeling, particularly in the filter’s resonance, saturation, and response to the incoming oscillator signal. Each Upper and Lower layer has its own independent filter and envelope, allowing the two layers to be shaped and animated differently within the same preset.
Voltage Controlled Filter Controls
Cutoff
Function: Sets the frequency above which the filter begins reducing high-frequency content.
Sound: Higher settings allow more harmonics to pass, producing a brighter and more open tone. Lower settings remove upper harmonics, making the sound darker, softer, and more rounded.
At its highest settings, the filter is effectively open for most sounds. At very low settings, only the deepest frequencies may remain.
Interactions: Cutoff establishes the filter’s starting point. The Filter Envelope, KB Track, Velocity, modulation, and Emphasis all work relative to this setting.
Cutoff and Contour Amount are especially important partners. If Cutoff is already fully open, the envelope may have little room to move it any higher. Lowering Cutoff gives the envelope space to create a more audible sweep.
Tip: When a filter envelope doesn’t seem to be doing much, lower Cutoff before increasing Contour Amount. The envelope may be working perfectly well but have nowhere left to go.
Emphasis
Function: Adds feedback around the filter’s cutoff frequency. This is more commonly called resonance.
Sound: Low settings add subtle definition and a gentle peak around the cutoff point. Moderate settings create more obvious brightness, hollowness, and vocal-like coloration. High settings produce a sharp resonant whistle and can drive the filter into self-oscillation.
At self-oscillation, the filter generates a sine-like tone of its own, even when the oscillator levels are turned down.
Interactions: The frequency of the resonant peak follows Cutoff. Moving Cutoff therefore changes both the brightness of the oscillator signal and the pitch of the resonance.
High Emphasis settings can reduce the apparent weight of frequencies below the cutoff point. The adjacent Emphasis Compensation button provides an alternate response when you want to preserve more body.
Tip: For basses and leads, try moderate Emphasis rather than immediately pushing it toward self-oscillation. A smaller resonant peak often adds useful definition without thinning the sound or overpowering the oscillators.
Emphasis Compensation
Function: Compensates for the perceived loss of level and low-frequency weight that can occur as Emphasis is increased.
Sound: With compensation disabled, raising Emphasis produces a more traditional ladder-filter response, in which the resonant peak becomes increasingly prominent while the body of the sound may recede.
With compensation enabled, more of the underlying fullness is retained as Emphasis rises.
Interactions: The difference becomes more noticeable at higher Emphasis settings. At low settings, the two modes may sound quite similar.
Emphasis Compensation doesn’t simply raise the output level. It changes the balance between the resonant peak and the frequencies beneath it.
Tip: Enable Emphasis Compensation when programming resonant basses, low leads, and sequences that need to retain their weight. Disable it when you want a leaner resonant sweep with a more exposed peak.
Contour Amount
Function: Sets how strongly the Filter Envelope modulates the cutoff frequency.
Sound: Low settings produce little or no automatic filter movement. Higher settings create a wider upward sweep as the envelope moves through its Attack, Decay, Sustain, and Release stages.
Interactions: Contour Amount works additively with Cutoff. Cutoff sets the filter’s resting position, while Contour Amount determines how far the envelope can push it upward.
The audible result also depends on the oscillator waveform. Bright ramp and narrow pulse waves make filter movement easy to hear. Triangle waves may respond more subtly because they contain fewer upper harmonics.
Tip: For a classic analog pluck, lower Cutoff, raise Contour Amount, use a fast Attack, short Decay, low Sustain, and short Release. Adjust Cutoff and Contour Amount together until the attack has the right amount of snap.
KB Track
Function: Causes the filter cutoff frequency to rise as higher notes are played.
Sound: At low settings, the filter remains near the same frequency across the keyboard, so high notes may become progressively darker. Increasing KB Track keeps upper notes brighter by opening the filter as pitch rises. Higher settings make the filter response feel more closely connected to keyboard pitch, while lower settings preserve a more fixed cutoff position.
Interactions: KB Track adds to the base Cutoff setting and any movement created by the Filter Envelope. Its effect is most obvious when Cutoff is low enough to remove a noticeable amount of high-frequency content. With high Emphasis, KB Track also causes the resonant peak to rise in frequency as higher notes are played.
Tip: Use moderate KB Track on pads, brass, and polyphonic patches to keep chords balanced across the keyboard. For dark basses, use less tracking so the low register remains heavy and upper notes don’t become excessively bright.
Slope: 12 dB and 24 dB
Function: Selects how steeply the filter reduces frequencies above the cutoff point.
12 dB
Sound: Brighter, smoother, and more open. The shallower slope allows more upper-frequency content to remain above the cutoff point.
Use it for pads, strings, polyphonic brass, layered sounds, and patches that need filtering without becoming too dark.
24 dB
Sound: Darker, stronger, and more focused, with a more pronounced interaction between Cutoff and Emphasis. This is the slope most closely associated with the original Memorymoog filter.
Use it for basses, leads, resonant sequences, percussion, and classic analog filter sweeps.
Interactions: The same Cutoff setting can sound substantially different in the two modes. Switching from 12 dB to 24 dB may require raising Cutoff slightly to preserve a similar degree of brightness.
Tip: Don’t think of 12 dB as merely the mild setting. Its shallower response can produce large, expensive-sounding pads because it preserves harmonic detail while still allowing the envelope to shape the tone.
Filter Envelope Generator
The Filter Envelope creates a changing control signal each time a note is played. That signal is applied to Cutoff according to the Contour Amount setting.
Each voice has its own Filter Envelope, so notes in a chord can progress through their contours independently.
The envelope follows four stages: Attack, Decay, Sustain, and Release. The envelope doesn’t produce sound by itself. It shapes the filter over time, turning a static oscillator tone into something that snaps, swells, opens, closes, or slowly unfolds.
Attack
Function: Sets how long the envelope takes to rise from its starting level to its maximum level after a note is played.
Range: Approximately 1 millisecond to 10 seconds.
Sound: Short settings create an immediate filter opening. Longer settings produce a gradual brightening or swelling effect.
Interactions: Attack movement is heard only when Contour Amount is raised and Cutoff leaves enough room for the envelope to open the filter further.
Tip: Use a fast Attack for basses, plucks, and percussion. Increase Attack for strings, pads, and sounds that slowly brighten after the note begins.
Decay
Function: Sets how long the envelope takes to fall from its maximum level to the Sustain setting.
Range: Approximately 2 milliseconds to 20 seconds.
Sound: Short settings create a quick, percussive drop in brightness. Longer settings produce a gradual change that can continue developing after the initial attack.
Interactions: The destination of the Decay stage is determined by Sustain. If Sustain is set to maximum, there may be little or no audible decay.
Tip: For analog brass, use a fast Attack, medium Decay, and moderate Sustain. The filter opens quickly, then settles into a slightly darker held tone.
Sustain
Function: Sets the Filter Envelope level maintained while a note remains held.
Sound: Low Sustain settings allow the filter to close substantially after the Decay stage. Higher settings keep the held portion of the note brighter. Unlike Attack, Decay, and Release, Sustain controls level rather than time.
Interactions: Sustain establishes the destination of the Decay stage and the starting point of the Release stage.
Tip: Use low Sustain for plucks and percussive sounds. Use moderate or high Sustain for pads, organs, and sustained leads that need to remain harmonically open while held.
Release
Function: Sets how long the Filter Envelope takes to return to its resting level after the note is released.
Range: Approximately 2 milliseconds to 20 seconds.
Sound: Short settings cause the filter to close quickly when the key is released. Longer settings allow the tone to continue darkening gradually during the release tail.
Interactions: Filter Release is easiest to hear when the VCA envelope also has enough Release time for the sound to remain audible. If the amplifier shuts off immediately, the filter may continue moving, but there will be nothing left to hear.
The shared Release button must be enabled for the Release knob to take effect.
Tip: Match the Filter and VCA Release settings for a natural, unified fade. Offset them deliberately when you want the sound to darken or brighten as it disappears.
Velocity
Function: Sets how strongly note velocity affects the filter cutoff response.
Sound: At zero, playing harder or softer doesn’t change the filter response. Higher settings allow stronger key strikes to produce a brighter, more open sound.
Interactions: Velocity works with Cutoff, Contour Amount, and the Filter Envelope. If the filter is already fully open, increased velocity may have little audible effect.
The response also depends on the velocity range produced by the connected MIDI controller or recorded MIDI performance.
Tip: Moderate Velocity settings can make a patch feel expressive without becoming unpredictable. Try it on brass, electric-piano-like sounds, basses, and leads so softer notes remain round while harder notes cut through.
Shared Envelope Controls
The five switches positioned between the Filter and VCA envelopes affect both envelope generators. They determine how the envelopes retrigger, respond across the keyboard, enter their Release stages, and react to sustain-pedal messages.
Because these controls operate on both envelopes simultaneously, they can significantly change the feel of a patch even when the individual Attack, Decay, Sustain, Release, and Velocity settings remain unchanged.
Return To Zero
Function: Determines where the Filter and VCA envelopes begin when a voice is retriggered before its current envelope cycle has finished.
With Return To Zero disabled, a retriggered envelope begins from its current level. With Return To Zero enabled, it resets to zero before beginning the new Attack stage.
Sound: Disabling Return To Zero creates smoother transitions between rapidly repeated notes because the envelopes continue from their current levels.
Enabling it gives each retrigger a more clearly defined beginning, producing a sharper and more consistent attack.
Interactions: The difference is most noticeable with longer Attack or Release settings and when notes are played or repeated quickly. With very short envelope times, the two modes may sound similar.
Tip: Enable Return To Zero for punchy basses, brass, percussion, and sequences that need a consistent attack on every note. Disable it for flowing pads, legato lines, and patches where repeated notes should connect more smoothly.
Unconditional Contour
Function: Causes both envelopes to complete their contours without waiting for the key to be released.
When disabled, the envelopes move through Attack and Decay, remain at the Sustain level while the note is held, and enter Release when the key is released.
When enabled, the envelopes complete the Attack stage and proceed directly into Release, regardless of how long the key remains held. This effectively changes them from ADSR envelopes into simpler attack-and-release contours.
Sound: Notes become less dependent on how long keys are held. A quick tap and a long press can produce the same basic contour, making the sound behave more like a triggered event than a continuously held note.
Interactions: Unconditional Contour affects both brightness and volume because it controls the Filter and VCA envelopes together. Attack and Release become the primary controls for shaping the contour.
Tip: Use Unconditional Contour for percussion, struck or plucked sounds, repeating sequencer patterns, and effects that should complete a predictable contour with each trigger.
Keyboard Follow
Function: Shortens the Attack, Decay, and Release times of both envelopes as higher notes are played.
Sound: Lower notes retain slower, broader contours, while higher notes respond more quickly. This can make a patch feel more naturally balanced across the keyboard, much as many acoustic instruments respond more quickly in their upper registers.
Interactions: Keyboard Follow changes envelope timing, not filter brightness. It shouldn’t be confused with the filter’s KB Track control, which raises the cutoff frequency as higher notes are played.
Because it affects both envelopes, upper notes can become faster in both their tonal development and volume contour.
Tip: Try Keyboard Follow on piano-like, mallet, plucked-string, and orchestral patches. It can prevent high notes from feeling sluggish when the lower register uses relatively long envelope settings.
Release Button
Function: Enables or disables the Release stages of both the Filter and VCA envelopes.
With Release enabled, releasing a key causes each envelope to fall according to its Release knob setting. With Release disabled, the Release controls are bypassed and the envelopes end immediately when the note gate is removed.
Sound: Enabling Release allows notes to fade naturally after the keys are released. Disabling it produces a tighter, more abrupt ending.
Interactions: A long Filter or VCA Release setting won’t be heard when the Release button is disabled.
The button also works with Sustain Pedal behavior. When sustained notes are finally released, the envelopes enter their Release stages only if Release is enabled.
Tip: Disable Release for tight basses, clipped sequences, and sharply articulated parts. Enable it for pads, leads, strings, and sounds that should continue fading after the keys are released.
Sustain Pedal
Function: Enables the Filter and VCA envelopes to respond to incoming MIDI sustain-pedal messages.
With Sustain Pedal enabled, pressing the pedal keeps released notes sustained as though their keys were still held. When the pedal is released, the envelopes proceed into their Release stages.
With Sustain Pedal disabled, incoming sustain-pedal messages don’t hold the envelopes.
Sound: This allows chords and notes to overlap without requiring the keys to remain held. Depending on the envelope settings, it can produce anything from piano-like sustain to large overlapping pads and slowly accumulating harmonic clouds.
Interactions: The final fade after the pedal is released depends on the shared Release button and the individual Filter and VCA Release settings.
Long pedal holds can also consume additional voices as new notes are played. Each layer supports up to 16 voices, so dense sustained passages may eventually cause older notes to be reassigned.
Tip: Enable Sustain Pedal for pads, strings, layered keyboard sounds, and evolving textures. Disable it for sequenced basses or tightly articulated parts when pedal messages would blur the pattern.
Sound Design Tips
Start with Cutoff and Contour Amount
These two controls establish most of the filter envelope’s behavior. Lower Cutoff until the raw oscillator sound becomes noticeably darker, then raise Contour Amount until the envelope opens it by the desired amount. Only after that should you fine-tune the envelope times. This is usually faster than adjusting every control at once and hoping they eventually reach an agreement.
Use Slope to Separate the Layers
Set one layer to 24 dB for a dark, solid foundation and the other to 12 dB for a brighter, more open texture. Even when both layers use similar oscillator settings, the different slopes help them occupy distinct tonal roles. This works especially well for layered pads, brass, and composite bass sounds.
Preserve Bass with Emphasis Compensation
For a resonant bass, choose the 24 dB slope, lower Cutoff, and increase Emphasis until the resonant peak becomes clearly audible. Engage Emphasis Compensation to retain more low-frequency weight beneath it. Disable compensation afterward and compare. The leaner response may work better when the bass needs to leave room for a kick drum.
Make Resonance Playable
Raise Emphasis toward self-oscillation, reduce the oscillator Mixer levels, and increase KB Track. The resonant filter can become a pitched tonal element that follows the keyboard. Adjust Cutoff and KB Track by ear. This technique is useful for sine-like leads, whistles, electronic percussion, and layered tones.
Add Filter Snap Without a Full Sweep
Set Attack very fast, Decay short, Sustain moderately high, and Contour Amount fairly low.The filter will produce a brief bright accent at the beginning of each note, then settle quickly into the body of the sound. This adds articulation to basses, brass, and leads without creating an obvious sweep.
Let the Filter and Amplifier Envelopes Differ
The Filter and VCA envelopes don’t need identical settings. A longer Filter Release can allow a sustained tail to become progressively darker. A shorter Filter Release paired with a longer VCA Release creates a muted, receding decay. A slower Filter Attack than VCA Attack lets the note begin softly and brighten after its volume has already arrived. Small differences between the two envelopes often make a patch feel more organic than perfectly matching settings.
Note Regarding Actual Values in Memorymode 2
You may notice that the values displayed in the pop-up Tooltips, especially the time values for the envelopes (Attack, Decay, Sustain, and Release) do not match the labels as shown on the UI. This is not an error. During our reanalysis of the Memorymoog hardware for Memorymode 2, we found that actual curves and timings of the hardware do not precisely match what was labeled. We chose to keep the labels as they were on the original, but the tooltip values precisely match the actual behavior of what you will see and hear on both the hardware and in Memorymode 2.