k2k audio A single spectrogram can tell many different stories depending on how you color it. Color modes re-paint the same data to reveal amplitude, pitch, transients, phase damage, or harmonic structure — like switching between X-ray, infrared, and visible light on the same scene.
Instant Modes
Computed per frame, these update in real time as you explore. No waiting.
Amplitude
What it reveals The raw loudness of every frequency at every moment — the foundational view of your sound.
When you’d switch to it This is the default. Come back to it whenever you need a clear, uncluttered read on where the energy lives in your audio.
Quick example
- Load a vocal recording.
- Switch to Amplitude (or stay — it’s already selected).
- Bright teal-yellow regions mark the loudest vowel formants.
- Dark areas show the silence between phrases.
- Any bin approaching 0 dB flashes red, flagging possible clipping.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| dBFS | Normalize the display to peak level, so the loudest point reads 0 dB | On / Off | Off |
Color mapping Near-black is silence. As energy rises, color moves through teal into bright yellow. Bins that push past -0.5 dB turn red — a quick visual cue that you’re hitting the ceiling.
Frequency Bands
What it reveals A three-way split of the spectrum into bass, mids, and highs, painted in distinct colors so you can instantly see the balance of a sound.
When you’d switch to it You want a fast read on tonal balance — for instance, checking whether a kick drum is bleeding into the midrange, or whether a synth pad is top-heavy.
Quick example
- Load a full mix.
- Switch to Frequency Bands.
- The low end glows red, mids appear green, highs show as cyan-blue.
- A vocal sitting cleanly in the mids appears as a solid green stripe.
- Adjust Bass Cutoff or Mid Cutoff to shift the boundaries and match your mixing context.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Bass Cutoff | Frequency boundary between bass and mid regions | 20 — 20 000 Hz | 250 Hz |
| Mid Cutoff | Frequency boundary between mid and high regions | 20 — 20 000 Hz | 4 000 Hz |
Color mapping Three fixed colors: red for bass (below Bass Cutoff), yellow-green for mids (between the two cutoffs), and cyan-blue for highs (above Mid Cutoff). Every bin gets one of the three — no gradients, just a clean categorical split.
Pitch Class
What it reveals The musical note name of every frequency bin, painted in one of twelve colors (C through B), regardless of octave.
When you’d switch to it You’re hunting for a specific note — isolating the key of a drone, finding which pitch a resonance sits on, or checking whether a detuned partial has drifted to a neighboring note.
Quick example
- Load a piano chord.
- Switch to Pitch Class.
- Each harmonic series lights up in its root note’s color.
- A C root and its harmonics all share the same red hue across octaves.
- Toggle individual notes off in the filter to isolate just the E and G, seeing the chord’s third and fifth by themselves.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Tuning | Reference frequency for A4, shifts all note boundaries | 400 — 480 Hz | 440 Hz |
| Harmonic Width | How wide (in semitones) each pitch class “claims” around its center | 0.1 — 2.0 st | 1.0 st |
| Pitch Class Filter | Twelve toggle buttons (C through B) — switch individual notes on or off | Per-note on/off | All on |
Color mapping Twelve distinct colors, one per note: red (C), salmon (C#), orange (D), gold (D#), yellow-green (E), green (F), teal (F#), cyan (G), sky blue (G#), blue (A), indigo (A#), violet (B). Disabled notes in the filter go dark.
Spectral Flux
What it reveals Frame-to-frame magnitude change — bright wherever something just moved, dark wherever the spectrum is steady.
When you’d switch to it You want to see where the action is: note onsets, percussive hits, sudden timbral shifts. Sustained tones fade to black, so transient detail pops out.
Quick example
- Load a drum loop.
- Switch to Spectral Flux.
- Each kick and snare hit flares bright across its frequency range.
- Hi-hat taps appear as narrow bright flashes in the highs.
- Lower the Threshold to widen sensitivity and catch softer ghost notes.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Threshold | Sensitivity of change detection — maps to a 0—48 dB range internally | 0.00 — 1.00 | 0.50 |
Color mapping Same continuous ramp as Amplitude: near-black means nothing changed, teal means moderate movement, bright yellow means a large magnitude jump between frames.
Onsets
What it reveals Per-bin onset detail — pinpoints exactly where new energy appeared, with finer temporal resolution than Spectral Flux.
When you’d switch to it You need precise onset locations across the spectrum: aligning a sample to a grid, checking whether a transient is smeared across too many frames, or verifying that a noise gate opened cleanly.
Quick example
- Load a fingerpicked guitar.
- Switch to Onsets.
- Each pluck shows as a sharp vertical bright line at the moment the string is struck.
- Raise Sensitivity to catch the quieter hammer-on notes.
- Shorten Duration to tighten the onset window and separate closely spaced notes.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Sensitivity | How much spectral flux is needed to register as an onset | 0.00 — 1.00 | 0.50 |
| Duration | Length of the onset detection window | 5 — 100 ms | 10 ms |
| Min Interval | Minimum time between two consecutive onsets | 10 — 500 ms | 50 ms |
Color mapping Continuous ramp from near-black (no onset) through teal to bright yellow (strong onset). Only positive energy increases register — decay and silence stay dark.
Temporal Envelope
What it reveals Short-term energy per frequency bin over a sliding window, making rhythmic pulse and amplitude modulation visible across the spectrum.
When you’d switch to it You want to see the rhythmic shape of a sound — the pump of a sidechain compressor, the tremolo rate on a pad, or the natural amplitude envelope of a bowed string.
Quick example
- Load a synth pad with a tremolo effect.
- Switch to Temporal Envelope.
- The modulation appears as a pulsing brightness pattern across the harmonics.
- Increase Smoothing to blur fast jitter and reveal the underlying rhythm.
- Decrease Smoothing to catch faster amplitude changes like vibrato depth variations.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Smoothing | Length of the RMS averaging window | 1 — 500 ms | 50 ms |
Color mapping Continuous ramp: near-black for silence, teal for moderate energy, bright yellow for peaks. The smoothing window averages the brightness over time, so shorter windows look sharper and longer windows look gentler.
Spectral Centroid
What it reveals The spectral center of gravity at each moment — a single brightness value that tells you how “high” or “low” the overall timbral weight sits.
When you’d switch to it You’re tracking brightness over time: hearing a filter sweep and want to see it, comparing the tonal character of two takes, or checking whether a de-esser pushed the centroid down in the right frequency region.
Quick example
- Load a synth with a filter sweep from dark to bright.
- Switch to Spectral Centroid.
- The display starts dark (centroid is low) and brightens as the filter opens.
- Widen Bandwidth to soften the transition zone around the centroid.
- Narrow Bandwidth to get a tighter, more precise read on the center frequency.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Bandwidth | Width of the region around the centroid that receives full brightness | 50 — 2 000 Hz | 500 Hz |
Color mapping Continuous ramp: bins near the centroid glow bright (teal to yellow), bins far from the centroid fade to near-black. The Bandwidth parameter controls how quickly brightness falls off with distance from the center.