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.
Phase Observatory
A diagnostic toolkit for the invisible dimension. These modes reveal phase artifacts that are inaudible individually but degrade audio quality cumulatively — like hairline cracks you can only see under UV light.
Every Phase Observatory mode shares two global controls:
- View toggle — Absolute shows the raw diagnostic on its own. Compared highlights what changed between the node’s input and output, painting differences in amber so you can see exactly what your processing introduced or fixed.
- Sensitivity — Slides from conservative (only severe artifacts light up) to aggressive (every marginal anomaly appears). Start around 0.5 and raise it if the display looks too quiet.
Phasiness
What it reveals Metallic, hollow coloration caused by phase misalignment between overlapping signals or processing stages.
When you’d switch to it The mix sounds thin or flanged in a way you can’t pin down with EQ — like someone layered a slightly delayed copy underneath. Phasiness makes those cancellation zones visible.
Quick example
- Load a vocal that was recorded with two microphones at slightly different distances.
- Switch to Phasiness mode.
- Set the lens to Tonal Damage to focus on pitched content and ignore drum bleed.
- Bright regions in the spectrogram mark frequency bands where phase cancellation is eating your signal.
- Switch to Broadband to see the full picture, including noise and transient regions.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Lens | Tonal Damage (harmonic content only) or Broadband (all bins above floor) | — | Tonal Damage |
| Mag Floor | Ignores phase data in bins quieter than this threshold | -96 to 0 dB | -60 dB |
| Sensitivity | How small a phase deviation counts as damage | 0.00 - 1.00 | 0.50 |
Color mapping Dark background means clean phase. Damaged regions glow from deep magenta (mild) through to sky blue (severe). In Compared view, all differences appear on an amber ramp instead.
Cracks
What it reveals Micro-discontinuities in the phase spectrum — tiny jumps that produce subtle crackling or graininess, often buried under the main signal.
When you’d switch to it After spectral processing, time-stretching, or AI stem separation, the audio has a faint gritty texture that wasn’t there before. Cracks mode lights up the exact time-frequency locations where the phase broke.
Quick example
- Run a vocal through a pitch shifter, then load the result.
- Switch to Cracks mode.
- Start with the In Sustain lens to check the body of the vocal.
- Switch to At Attacks and adjust the Region slider to inspect onset boundaries where cracks tend to cluster.
- Use the All lens for a complete overview.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Lens | In Sustain (excludes onsets), At Attacks (onsets only), or All (no filtering) | — | In Sustain |
| Mag Floor | Ignores phase data in bins quieter than this threshold | -96 to 0 dB | -60 dB |
| Sensitivity | Detection threshold for phase discontinuities | 0.00 - 1.00 | 0.50 |
| Region | Width of the attack zone when using the At Attacks lens | 10 - 200 ms | 50 ms |
Color mapping Dark background means intact phase. Cracks glow from deep magenta (mild) through to sky blue (severe). In Compared view, differences appear on an amber ramp.
Clicks & Splices
What it reveals Pops, clicks, and discontinuities at edit boundaries — the kind of artifacts you get from careless crossfades, sample-level cuts, or automated splice points.
When you’d switch to it You’ve assembled a vocal comp or chopped a drum loop and there’s an intermittent pop you can hear but can’t find by zooming into the waveform. This mode paints each click as a bright vertical stripe at the exact frame where the splice failed.
Quick example
- Load a comped vocal take with several edit points.
- Switch to Clicks & Splices mode.
- Use the In Sustain lens first — clicks in sustained vowels are the most audible.
- Switch to At Attacks to check whether any edit points land right on a transient, and adjust Region to widen or tighten the attack window.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Lens | In Sustain (suppresses transient regions) or At Attacks (onset regions only) | — | In Sustain |
| Mag Floor | Ignores phase data in bins quieter than this threshold | -96 to 0 dB | -60 dB |
| Sensitivity | How small a boundary discontinuity counts as a click | 0.00 - 1.00 | 0.50 |
| Region | Width of the attack zone when using the At Attacks lens | 10 - 200 ms | 50 ms |
Color mapping Dark background means clean transitions. Splice artifacts glow from deep magenta (mild) through to sky blue (severe). In Compared view, differences appear on an amber ramp.
Wobble
What it reveals Pitch instability — the warbling, underwater quality that comes from inconsistent phase velocity across frames.
When you’d switch to it A synth pad or sustained note sounds like it’s gently swimming or detuning over time, but it shouldn’t be. Wobble mode separates fast instability (jitter) from slow drift so you can tell whether the problem is rapid flutter or a gradual wandering of pitch.
Quick example
- Load a held piano note that was time-stretched aggressively.
- Switch to Wobble mode.
- Set the lens to Jitter — bright streaks indicate rapid frame-to-frame phase instability.
- Switch to Drift to see whether the phase is also wandering slowly over the duration of the note.
- Raise Sensitivity if the display looks too dark.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Lens | Jitter (short 4-frame window, fast instability) or Drift (long 16-frame window, slow wandering) | — | Jitter |
| Mag Floor | Ignores phase data in bins quieter than this threshold | -96 to 0 dB | -60 dB |
| Sensitivity | How small a phase velocity variation counts as wobble | 0.00 - 1.00 | 0.50 |
Color mapping Dark background means stable phase. Wobble regions glow from deep magenta (mild) through to sky blue (severe). In Compared view, differences appear on an amber ramp.
Attack Smear
What it reveals Blurred transients — the loss of punch and definition that happens when attack energy gets spread across time or frequency.
When you’d switch to it Drums feel soft and diffuse after processing, or a plucked guitar has lost its initial bite. Attack Smear offers four separate scans to pinpoint whether the problem is pre-echo bleeding before the hit, frequency dispersion smearing the onset, temporal energy spread, or outright phase breaks at the attack boundary.
Quick example
- Load a drum loop that went through a codec or heavy spectral processing.
- Switch to Attack Smear mode.
- Start with the Pre-Echo scan — bright patches before each hit mean energy is leaking backward in time.
- Switch to Dispersion to check whether high and low frequencies arrive at different times.
- Try Smearing to see if the transient energy is spread too wide, then Phase Breaks for abrupt discontinuities at onset edges.
- Narrow the Focus range to isolate the mid frequencies (200-4000 Hz) where smearing is most audible.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Scan | Pre-Echo, Dispersion, Smearing, or Phase Breaks — four independent diagnostic views | — | Pre-Echo |
| Mag Floor | Ignores phase data in bins quieter than this threshold | -96 to 0 dB | -60 dB |
| Sensitivity | Detection threshold for smear artifacts | 0.00 - 1.00 | 0.50 |
| Region | Width of the attack zone around each detected onset | 10 - 200 ms | 50 ms |
| Focus Lo | Lower frequency bound for the analysis | 20 - 20,000 Hz | 20 Hz |
| Focus Hi | Upper frequency bound for the analysis | 20 - 20,000 Hz | 20,000 Hz |
Color mapping Each scan has its own color ramp so you can tell them apart at a glance. Pre-Echo glows amber, Dispersion glows teal, Smearing glows coral, and Phase Breaks glow chartreuse — all ramping from dark (clean) to bright (damaged). In Compared view, all four scans switch to the shared amber ramp.
Temporal Leak
What it reveals Group delay problems — energy arriving too early (pre-echo) or lingering too late (post-ringing) relative to where it should be in time.
When you’d switch to it After filtering, convolution, or any phase-heavy processing, the audio feels smeared in time — reverb tails seem to start before the hit, or transients have a ghostly shadow. Temporal Leak separates forward leak from backward leak so you can identify the direction of the problem.
Quick example
- Load audio that was processed through a steep linear-phase EQ.
- Switch to Temporal Leak mode.
- Set the lens to Forward Leak — bright regions mean energy is arriving early (pre-echo from the filter).
- Switch to Backward Leak to check for post-ringing and lingering tails.
- Adjust Range to set how much timing deviation (in milliseconds) fills the display — lower values make subtle leaks more visible.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Lens | Forward Leak (energy arriving early) or Backward Leak (energy lingering late) | — | Forward Leak |
| Mag Floor | Ignores phase data in bins quieter than this threshold | -96 to 0 dB | -60 dB |
| Sensitivity | How small a group delay deviation registers as a leak | 0.00 - 1.00 | 0.50 |
| Range | Group delay deviation range for normalization — smaller values reveal subtler timing differences | 1 - 50 ms | 10 ms |
Color mapping Dark background means on-time energy. Leaked regions glow from deep magenta (mild deviation) through to sky blue (severe deviation). In Compared view, differences appear on an amber ramp.
Timbre Shift
What it reveals Broken harmonic phase relationships — when the partials of a tone no longer line up the way they should, changing the perceived timbre even though the frequencies and amplitudes look correct.
When you’d switch to it A voice or instrument sounds “different” after processing — not wrong in pitch or level, but changed in character, as if played through a different body or room. Timbre Shift checks whether harmonics still hold their expected phase pattern or have drifted apart.
Quick example
- Load a vocal before and after AI stem separation (use Compared view).
- Switch to Timbre Shift mode.
- Set the lens to Harmonic Lock to see whether the inter-harmonic phase relationships are intact.
- Switch to Partial Drift to check whether those relationships are shifting over time — a sign of unstable resynthesis.
- Adjust Harmonics to scan more or fewer partials above the fundamental.
- Narrow Focus Lo / Focus Hi to concentrate on the vocal’s pitch range.
Parameters
| Parameter | What it controls | Range | Default |
|---|---|---|---|
| Lens | Harmonic Lock (static phase relationships) or Partial Drift (frame-to-frame change in those relationships) | — | Harmonic Lock |
| Mag Floor | Ignores phase data in bins quieter than this threshold | -96 to 0 dB | -60 dB |
| Sensitivity | How small a harmonic phase deviation counts as timbre damage | 0.00 - 1.00 | 0.50 |
| Harmonics | Number of harmonics above the fundamental to analyze | 4 - 32 | 16 |
| Focus Lo | Lower frequency bound for fundamental detection | 20 - 20,000 Hz | 20 Hz |
| Focus Hi | Upper frequency bound for fundamental detection | 20 - 20,000 Hz | 20,000 Hz |
Color mapping Dark background means harmonics are phase-locked as expected. Shifted regions glow from deep magenta (mild) through to sky blue (severe). In Compared view, differences appear on an amber ramp.