A live stereo visualizer and meter. Put it anywhere in a chain and it shows the signal from four angles at once, a spectrogram, a waveform, a frequency profile and a stereo field, while the audio passes through exactly unchanged.
The idea
Most problems in a mix are easier to hear once you can see them. Metergram lines its views up so they agree with each other: the spectrogram and the frequency profile share one logarithmic frequency axis, and the spectrogram and the waveform scroll on one time axis, so a column in one is the same moment in the other. A piano keyboard along the edge of the spectrogram shows which note each frequency band belongs to.
Nothing on screen touches the sound. Every display setting, from the colour scheme to the analysis method, changes only what you see.
WebGPU draws the default four graphs when available; Customize → Graph renderer switches to Canvas2D and remembers your preference. The GPU waveform keeps one peak envelope with a smooth RMS energy gradient and fractional scrolling. The stereo field defaults to a fine phosphor trace with restrained bloom. Views → Lower-right monitoring view → Stereo field style compares Fine phosphor, Density and Soft bloom; the waveform styles remain in the lower-left view settings. In Views → Lower-left signal view, choose LUFS blend to colour the waveform with measured momentary loudness. This starts the existing measurement; RMS colour is used while it collects its first 400 ms.
Views → Lower-right monitoring view also offers Mid/Side phosphor and Polar Level, alongside the original three L/R looks. Slow auto adjusts the common display gain gradually; Fixed keeps amplitude calibration. The scale multiplier is shown in the plot. Correlation (−1 to +1) always measures the original paired input. Mid/Side puts mono upright and opposite-phase audio across the horizontal; its GPU trace has a bright current core and dimmer green 350 ms afterglow. Polar Level folds the image into a semicircle and shows RMS amplitude per occupied angle with 80 ms attack/350 ms release smoothing. Its auto scale follows the ray envelope. Canvas2D retains a line/ray fallback.
The four panels
- Frequency history: a scrolling spectrogram, from 20 Hz to 20 kHz by default. Drag it up or down to move the band, scroll to zoom time.
- Frequency profile: the current spectrum, with optional octave smoothing and a peak-hold trace. Scroll on it to zoom the frequency range.
- Signal: a waveform history whose height is the peak level and whose colour shows loudness.
- Monitor: a stereo field showing balance, correlation and width.
Customize lets you swap any panel for another view, such as Mid/Side spectra, stereo correlation by frequency, loudness history, a triggered oscilloscope, or numeric level and loudness meters. You can also show Left, Right, or both channels stacked, choose the frequency range, the analysis resolution, colour palettes (Magma, Viridis, Cividis, Inferno) and how fast the history scrolls.
Freeze pauses the picture while audio keeps flowing; Clear wipes the history.
Loudness and reference
Start a measurement to get momentary, short-term and integrated loudness in LUFS, loudness range, true peak and peak-to-loudness ratio, measured on every sample even when the panel is closed or frozen. Measurements can be exported. These follow the standard loudness methods, but Metergram is not a certified broadcast meter.
Reference comparison captures the average spectrum of a reference track and overlays it, or the difference, on what is playing now, with automatic level matching.
The oscilloscope, reference capture and a few stereo history views need a host that supplies continuous audio history. Where it is missing, those views say so instead of guessing.
