MewFM

Independent of the FM per-OP EG (AR/DR/SR/RR/SL), MewFM provides a voice-wide AHDSR envelope, a SoftLFO, and a per-voice filter. These behave identically for both FM and SSG.

AHDSR (Volume Envelope)

Unlike a 4-stage ADSR, Sustain here is a level, not a time. The Hold stage lets you intentionally shape the attack plateau.

SoftLFO

Alongside the chip’s Hardware LFO, MewFM runs a software-based SoftLFO independently per voice. Each channel runs LFO1 to LFO4 in parallel, and each LFO has its own target / waveform / Freq / Depth / Delay.

Target list

FM only: using Op<N> TL targets

For example, with ALG 5 (OP1 → OP2/3/4 parallel carriers), routing LFO1 to Op1 TL makes the modulator OP1’s output rise and fall periodically, giving the whole tone a wah-like harmonic sweep.

Since the carrier/modulator role swaps depending on the algorithm, pick the target OP based on whether you want volume motion or timbre motion.

When to use ModWheel drive

If Drive is set to ModWheel, the LFO is silent while MW = 0. This is ideal for vibrato that you only apply mid-performance.

Per-voice filter

Each voice has a 2-stage cascaded biquad filter. The Cutoff can be modulated by both the AHDSR (Filter Envelope) and the SoftLFO.

CC 74 / 71 and the filter

CC 74 (Brightness) and CC 71 (Resonance) override the filter’s cutoff / Q in real time, but this is a temporary override — your saved preset values are not modified. The override is re-applied at each note-on.

VelMap / KeyMap

A per-parameter mechanism that adds an offset based on velocity and note number. Use it to make velocity-dependent timbres (“feel-the-touch”), or to give high-/low-register zones different character, the way realistic sampled instruments do.

VelMap and KeyMap sit side-by-side in the same dialog so you can edit both at once.

How to set it up

A small round dot (the Mod-Mapping dot) appears at the right edge of every slider that supports mapping. Click the dot to open the Velocity / Key Mapping dialog.

1. Click the dot on the right edge of the target parameter’s slider.
   • The left half of the dialog is Velocity Mapping; the right half is Key Mapping.
2. Type values directly into the fields:
   • Velocity Mapping (left)
     • @ velocity 0: offset applied at velocity 0.
     • @ velocity 127: offset applied at velocity 127.
     • Velocities in between (v = 1–126) are linearly interpolated.
   • Key Mapping (right)
     • Note LOW / Note HIGH: the MIDI note range in which the mapping applies (0–127).
     • Offset @ LOW / Offset @ HIGH: offsets at each end.
     • Notes outside the range are clamped to the LOW / HIGH value.
3. Use the buttons at the bottom to confirm:
   • Apply — apply the values and close the dialog.
   • Clear All — clear both the VelMap and KeyMap for this parameter.
   • Cancel — discard changes and close.

When VelMap is considered “active”

If either @ velocity 0 or @ velocity 127 is non-zero, the VelMap is treated as active for that parameter. With both at 0/0 it is automatically disabled.

Visual feedback

• When a mapping is active, the dot at the right of the slider lights up amber, and the slider track shifts to an orange tint.
• While a note is sounding, the value actually applied for that note and velocity is shown as a soft yellow overlay on top of the slider.

Just looking at the dot and the track tells you at a glance which parameters have a mapping, without opening anything.

Parameters that support mapping

Calculation model

At note-on, “base value + VelMap offset + KeyMap offset” is calculated and sent to the voice.

actual = base
       + lerp(atVel0,  atVel127, velocity / 127)
       + lerp(atLo,    atHi,     (note - noteLo) / (noteHi - noteLo))

Examples

Example 1: piano-style velocity response (VelMap)

Leave the carrier’s TL alone (0/0), and on the modulator OP’s TL set @ velocity 0 = +30 (soft strikes → more attenuation, weaker modulation) and @ velocity 127 = 0 (hard strikes → full modulation). As velocity rises, more upper harmonics appear and the attack becomes punchier — an acoustic-style touch response.

Example 2: heavier bass register (KeyMap)

On a modulator OP’s TL, set Note LOW = 24, Note HIGH = 72, Offset @ LOW = -10, Offset @ HIGH = 0. At low C1 (24) the TL is -10 (stronger modulation → thicker tone); from middle C5 (72) upward, the base value applies. Result: a thicker bass register while highs stay clean.

Example 3: faster EG in the upper register (KeyMap)

Setting Offset @ HIGH = +5 on AR or RR makes the EG faster higher up — useful for reproducing the quick high-register decay of pianos or bells (especially combined with KS).