MC-420 controls

Loops are the 20 pads in columns 2–5. Presets are the 10 pads in columns 0–1. LEDs: red blink recording, green playing, yellow blink paused, off empty.
Empty loop: press = ARM. Press again = FINISH. The take closes at its snapped length, and presses are ignored until then.
Loop with content: release toggles pause and play. Press does nothing. Hold 1 s erases it. Erasing the last loop resets the phrase length.
Presets: tap applies a set (yellow = saved). Hold 1 s saves the loops playing now. Erasing a loop removes it from presets.
Guitar [68] held + loop: toggles it as sidechain source. Other loops duck with its level.
Shuffle pads [15] [23] [31] [39]: tap = shuffle mode 1–4, tap again to clear. With Gate [7] held = gate mode. They also show the 16-beat phrase: dark idle, green while any loop plays, yellow for passed quarters, red for now.

SHIFT held while pressing a bank selects that bank’s SHIFT page until the bank is pressed again without SHIFT.
Dub: k1 gate amount, k2 gate pattern, k3 LFO rate, k4 LFO depth, k5 LFO shape, k6 LFO target, k7 LFO phase.
Guitar: k1–k4 filter attack, decay, sustain, release; k5–k8 amp attack, decay, sustain, release.
Lofi: k1 Resonode input (0 = keys self-sounding, 1 = live signal only); k2–k5 Resonode weights Percussive, Metal/Glass, Strings, Dance Bass; k6 tone 200–18000 Hz; k7 level; k8 couple.
Formant (k8 on Dub, CC 53): centre 60–68 is off, range ±1.5. Active only while live pitch is on, in multi-key mode, or while a pitch-lock key is held.

[69] tap toggles the granulator (green = on). It layers a grain cloud from the live input under everything else.
SHIFT + [69] toggles Resonode (red blink = on). Toggling Resonode also turns the granulator off.
Lofi knob page follows SHIFT on the last Lofi press, not whether Resonode is on. A plain tap shows the granulator page even while Resonode stays on.
Keys (channel 2): with Resonode on, keys play 4 Resonode voices. Else a key with a sample loaded plays it. Otherwise the 6-voice pitch-lock lands the output on the held key and replaces the input. Velocity sets loudness.
[64] transpose toggles live pitch (lit = on). While on, the mod wheel (CC 1, ±12 semitones, centre dead) and CC 52 (0–127 = −12 to +12) bend pitch. A pitch-lock key press also turns it on.
SHIFT + [64] toggles multi-key mode (yellow blink). Mod wheel and CC 52 are ignored, and key presses do not turn live pitch on.
Sustain pedal (CC 64) holds keys. SHIFT + press latches.
[70] / [71] half / double speed while held. [81] stops all loops while held. SHIFT + [81] stops immediately: takes close and every loop pauses.
[65] held records a sample; release stops. [66] held records a drum hit into each key pressed; release [66] stops.

Record is ARM and FINISH on a loop pad (section 1). [93] Record exports a clip to the USB drive.
First take after boot sets the phrase, its length in beats. With no Link peers it sets the session tempo to the whole-beat tempo nearest 120 BPM (60–240). With peers, the phrase is whole beats at the session tempo.
Later takes snap to a power-of-two beat grid inside the phrase. Within 0.4 beat of 1 becomes 1. A take that overshoots its grid point by up to 1 beat is cut back to it. Otherwise it runs to the next grid point. A take shorter than two phrases never exceeds one phrase.

Hold Play [91] = CLEAR ALL. On press every DSP setting returns to its default. All loops, presets, pitch-lock and Resonode voices, the Resonode latch and the phrase length are cleared. The audio wipe runs while Play is held.

A loop is one take on its own pad. Release pauses or resumes it without changing its length. A loop with content must be erased (hold 1 s) before its pad records again. A take started with SHIFT held pauses the other playing loops when it finishes.