Live mode

The knob explorer. Every other measurement is a photograph; live mode is video. The app plays a very short measurement sweep on repeat and re-reads the pedal’s harmonic recipe from each one, about three times a second — so you can turn a knob and watch the harmonic recipe move under your hand. Found the setting? Snapshot it into the library.

What it shows

PedalScope plays a very short measurement sweep on repeat (about 3 per second) and re-reads the pedal’s harmonic recipe from each one. The bars are the harmonics the pedal adds, read at the probe note; THD is their combined loudness. A knob turned mid-sweep briefly flags the reading — wait for the border to clear, then snapshot to save the setting to the library. Tone mode trades the band picture for speed: a steady tone at the probe note with harmonics tracked ~12 times a second.

Alongside the bars, the H1 mini-curve shows the pedal’s tone shaping (its EQ) updating live — sweep a filter knob and you’ll see the curve tilt in real time.

Sweep vs. tone

The mode control picks between two ways of listening:

Sweep (the default) repeats a short measurement sweep, so every update is a whole-band harmonic recipe: bars at the probe note, the H1 EQ curve, and a snapshot-able measurement, about three times a second.
Tone plays a steady tone at the probe note and tracks its harmonics directly (a Goertzel bank at each multiple of the note), about twelve times a second — the fastest knob feel the app has. The trade: one pitch only, so there’s no EQ curve and nothing band-wide to snapshot; switch back to sweep mode to capture what you found. The probe is snapped a hair (at most half an analysis bin, a few cents) so the analysis reads exact bins — the footer under the bars shows the exact frequency playing.

Changing the probe note while live in tone mode restarts the tone at the new pitch after a brief gap — that’s the stimulus changing, not a glitch.

The bars are read against the note itself: the top of the chart is 0 dB, as loud as the note, and each bar hangs down to its harmonic’s level. A harmonic louder than the note — an octave-up effect’s second harmonic, say — cannot be drawn on that scale, so its bar is capped at the top with an orange band and its label carries a ▲ and the true value (▲ +12 means 12 dB above the note). The scale does not stretch to fit: it stays still while you turn knobs.

Peak hold leaves a fading ghost tick at each bar’s recent maximum (about two seconds of decay), so a before/after knob turn reads at a glance: the ghost is where the harmonic was, the bar is where it is now. It’s a display aid only — snapshots always save the measured values, never the ghosts — and the checkbox under the bars turns it off.

The readouts and flags

THD at the probe note — the one-number dirt meter, updating as you tweak. Change the probe note to hear/see the pedal at different registers.
Update rate — sweeps per second, normally ≥ 2 Hz. If it drops, the analysis is falling behind (rare; close other heavy apps).
Confidence — how far the harmonic pulses stand above the measurement floor, in dB. High numbers mean the bars are trustworthy; when it sags, treat small bar differences as noise. It does not check that the sweep was read in the right place — a correctly read octave device can score as low as a misread bare cable — which is why that has its own check, below.
Dropouts — capture samples lost mid-stream. Occasional small counts self-heal (the engine resynchronizes); persistent growth means the interface is struggling at this buffer size.
The red border means the current reading is invalid, with the reason spelled out: interface clipping (lower the level or input gain), no signal (check cables and input channel), the level changed mid-sweep (just settling — it clears itself), or the response is not where the calibration puts it (next section). Displayed bars freeze on the last good reading rather than showing garbage.

When the calibration’s latency is wrong

Live mode cuts each sweep out of the incoming audio at the loop latency the selected calibration measured, and then checks every sweep it cuts: the response’s loudest part has to sit where the analysis reads a harmonic. Across the clippers, rectifiers and filtered devices it was measured on, every harmonic read stays within 1 dB while the response sits within 1.3 ms of that place; past that, the frame is refused. The border turns red, the bars stop updating, Snapshot stays disabled, and the page says what it found — where the response actually arrives and what the calibration (named by its date and time) says, in samples and milliseconds.

Without the check, a calibration off by 28 ms produced a bare cable reading thousands of percent of distortion, with a second harmonic 37 dB louder than the note, at a confident 58 dB. Nothing in that calibration’s flatness, floor or gain revealed it.

A calibration can carry the wrong latency without looking wrong:

It was made while another audio app was running. A background audio utility can add tens of milliseconds to the loop, and the calibration records that. Quit the utility and the loop is faster than the calibration says.
It belongs to another interface. Each interface has its own latency and its own loop response. Live mode’s default calibration is the newest one made on the interface you have selected; changing the interface picks again and says what it picked, or that the library holds no calibration of that interface. Another interface’s calibrations stay in the picker, labeled as another interface’s, and are never chosen for you.
Something in the loop adds its own delay. A digital effect with more than about a millisecond of processing latency moves the response by that much, whatever the calibration says.

The remedy is the same for all three: recalibrate with the loop exactly as it is now, and choose that calibration. The Measure pane’s Harmonic Distortion measurement finds the sweep in each capture itself, so it is not exposed to this. Live mode cuts at a fixed point, and so checks that point instead.

Snapshots

The Snapshot button freezes the most recent complete, valid harmonic recipe into the library (a Live snapshot under the pedal) — the raw measurement, not the smoothed display. Pick the pedal — Live Mode starts on the pedal selected in the sidebar, as New Measurement does, except a pedal bound to a plugin (Live mode captures from the interface, so it starts on new pedal… instead) — set the variant picker to match the panel (variants), and the record files itself with a canonical settings label, ready to compare against full measurements.

Why the level stops at −12 dBFS

Live mode only drives the pedal as hard as the loopback calibration verified the interface can take. Louder would risk clipping the interface, which corrupts every reading.

The same logic caps the quiet end (−50 dBFS): below it, the short sweep sinks toward the noise floor and confidence collapses.

Common misreadings

Live bars are a reduced measurement. The repeating sweep is short (~0.36 s) and band-limited (60 Hz–5 kHz, harmonics H2–H5) so it can update fast. Expect small offsets against a full Harmonic Distortion measurement of the same setting — the snapshot records are honest about their live provenance for exactly this reason. For the archival version of a setting you love, run a full measurement.
The bars are smoothed for your eyes (a fast exponential average that settles within two frames). The morphing is display-side only; snapshots are never smoothed.
A calm display isn’t proof of a calm pedal — between sweeps the pedal is unobserved. Circuits that gate, sputter, or bloom slowly show their character better in a full Gain Map.

Open it from the toolbar, or: go live.