Match a Reference Track

This page compares a mix with a commercial reference, measures loudness and tonal balance, applies a stereo-safe correction, and measures again. Reference matching changes tone and gain; it does not change arrangement, performance, or mix balance.

What You Will Learn

By the end of this page you should be able to:

• measure the loudness and tonal gap between a mix and a reference before touching either file;
• read a four-band tonal-balance deviation and recognize when its shape calls for a tilt, a pair of shelves, or a full parametric EQ;
• apply that correction through the entry point that keeps your stereo pair intact, instead of the pair commands that fold to mono first;
• state plainly what reference matching does not do.

The whole job

#!/usr/bin/env bash
set -euo pipefail

# 1. Characterize the reference on its own terms.
sonare mastering-profile reference.wav --json

# 2. Measure the loudness gap between mix and reference.
sonare mastering-pair-analyze mix.wav --reference reference.wav \
  --analysis match.referenceLoudness --json

# 3. Measure the tonal gap, band by band.
sonare mastering-pair-analyze mix.wav --reference reference.wav \
  --analysis match.tonalBalance --json

# 4. Apply the correction on the stereo pair, not a mono downmix.
sonare mastering-processor mix.wav --processor eq.tilt \
  --params "tiltDb=4" -o tilted.wav --json

# 5. Confirm it closed both gaps.
sonare mastering-pair-analyze tilted.wav --reference reference.wav \
  --analysis match.tonalBalance --json
sonare mastering-pair-analyze tilted.wav --reference reference.wav \
  --analysis match.referenceLoudness --json

Measure, diagnose, correct, confirm

Everything up to the diagnosis is measurement; the mix is only touched once, and re-measuring afterward is what turns a guess into a confirmed correction.

Step 1 — Characterize the reference on its own terms

Before comparing anything, find out what the reference actually is:

sonare mastering-profile reference.wav --json

{
  "duration_sec": 183.20,
  "bpm": 119.88, "bpm_confidence": 0.70,
  "loudness": { "integrated_lufs": -24.56, "true_peak_db": -7.62,
                "crest_factor_db": 17.95, "lra_lu": 6.07 },
  "spectral": { "centroid_hz": 2555.14, "rolloff_hz": 5531.35,
                "sub_rms_db": 11.07, "low_rms_db": 21.40, "air_rms_db": -14.28 },
  "dynamics": { "short_term_lufs_std": 3.21, "attack_density": 4.15,
                "sustain_ratio": 0.58 },
  "defects": { "measured": false }
}

The CLI renders the binding's camelCase profile keys as snake_case. One call gives you tempo, loudness, spectral shape, and dynamics for the file you are chasing — the same measured fields Mastering Assistant profiles for your own mix. Read this before the comparison: a reference at -24.56 LUFS integrated is quiet by streaming standards, which matters later when you decide whether to actually chase its loudness or just its tone.

Three of those loudness fields are what the meter below reports on a playing clip: integrated LUFS is the single number the next step will compare against your mix, true peak is the ceiling, and LRA is how far the loudness moves over the programme. A reference with a wide LRA hides a lot of motion behind its one integrated figure — matching that figure alone will not make your mix move the same way.

METERS · LOUDNESSIDLE

Loudness metering — LUFS, true-peak, and range

Scroll to load

The bar tracks momentary loudness as the clip plays; the panel is the loudness over time. Integrated LUFS is the single overall number, true-peak estimates peaks between samples, and LRA captures how much the loudness moves. Switch the window to compare the fast momentary meter with the smoother short-term one — each reports only once its window has filled, so the short-term contour starts three seconds into the clip.

Window

Step 2 — Measure the loudness gap

sonare mastering-pair-analyze mix.wav --reference reference.wav \
  --analysis match.referenceLoudness --json

{ "gain_to_match_db": -1.70, "reference_lufs": -24.56, "source_lufs": -22.86 }

gain_to_match_db is the gain that lands the source on the reference's loudness: source_lufs + gain_to_match_db = reference_lufs. Here the mix is 1.7 dB hotter than the reference, so a negative number brings it down to match.

Matching loudness is not the same as choosing a target

This number says "your mix and the reference differ by 1.7 dB," not "master to -24.56 LUFS." A reference pulled from a different era or platform can sit well off a current delivery target — see Delivery Targets before treating reference_lufs as the number to land on.

Step 3 — Measure the tonal gap, band by band

sonare mastering-pair-analyze mix.wav --reference reference.wav \
  --analysis match.tonalBalance --json

{
  "bands": [
    { "low_hz": 20,    "high_hz": 250,   "reference_db": 14.40,  "source_db": 16.39,  "deviation_db": 2.00 },
    { "low_hz": 250,   "high_hz": 2000,  "reference_db": -1.62,  "source_db": -1.73,  "deviation_db": -0.11 },
    { "low_hz": 2000,  "high_hz": 8000,  "reference_db": -14.36, "source_db": -16.33, "deviation_db": -1.97 },
    { "low_hz": 8000,  "high_hz": 20000, "reference_db": -14.54, "source_db": -16.54, "deviation_db": -2.00 }
  ]
}

deviation_db is source_db - reference_db: positive means the mix runs hotter than the reference in that band. Reading down the table, the shape is unmistakable — the mix is about 2 dB hot at the bottom, roughly matched through the low-mids, and about 2 dB dark across everything above 2 kHz. That is not four independent problems; it is one problem, seen through four windows.

For finer resolution than four bands, match.tonalBalanceLogBands reports the same deviation across 32 log-spaced bands, and match.matchEqCurve returns a full frequency-response correction curve rather than a banded summary — the shape Reference Match's browser demo works from directly.

Step 4 — Pick the correction: tilt, shelf, or full EQ

A deviation that swings smoothly from positive at one end to negative at the other, crossing zero once, is a tilt — a single pivot with the low side and the high side moving in opposite directions. That is exactly eq.tilt's job: one tiltDb knob and a pivotHz (1000 Hz by default), applied through mastering-processor.

Read the tilt amount off the two extreme bands: the low band needs about -2 dB, the high band needs about +2 dB, so tiltDb ≈ (low-band deviation) - (high-band deviation) = 2.00 - (-2.00) = 4.0. Treat that as a starting point, not a final answer — the whole reason for Step 6 is to confirm it rather than trust the arithmetic.

Two other tools are usable here, and each fits a different deviation shape:

• eq.shelving applies an independent low shelf and high shelf, each with its own corner frequency and gain. Reach for it when the low and high corrections do not share one sensible pivot — for example when the low end needs trimming below 250 Hz but the lift should only start above 8 kHz, not at 1 kHz. Run against this fixture (lowFrequencyHz=250, lowGainDb=-2, highFrequencyHz=2000, highGainDb=2) it closed the gap to 0.27 / 0.12 / -0.13 / -0.001 dB — good, but not as clean as the tilt, because two shelves cannot reproduce one continuous slope exactly.
• eq.equalizer is a full parametric EQ with up to two dozen bands (band0.* through band23.*), each independently typed as peak, shelf, or tilt. Reach for it when the deviation is not tilt- or shelf-shaped at all — a narrow dip or peak sitting inside one of the four tonal-balance bands, which neither a single pivot nor two shelves can isolate.

This fixture's deviation is a clean tilt, so eq.tilt is the right tool and the one this page carries through.

Step 5 — Apply it on the stereo pair

sonare mastering-processor mix.wav --processor eq.tilt \
  --params "tiltDb=4" -o tilted.wav --json

{ "processor": "eq.tilt", "input_lufs": -19.61, "output_lufs": -21.31,
  "applied_gain_db": 0.0, "sample_rate": 48000, "output": "tilted.wav",
  "stereo": true }

"stereo": true is the field to check. mastering-processor decides its entry point from the source file's own channel count — a stereo mix.wav takes the stereo path automatically, for eq.tilt or any other solo processor, with no flag to remember.

mastering-pair-processor folds to mono; mastering-processor does not

The pair commands are a different code path, and they downmix unconditionally:

sonare mastering-pair-processor mix.wav --processor match.applyMatchEq \
  --reference reference.wav -o matched.wav --json
# warning: 2-channel input is downmixed to mono by this CLI command
# {"processor": "match.applyMatchEq", "input_lufs": -22.86, "output_lufs": -24.40, ...}

matched.wav comes out with channels: 1. Re-measuring match.tonalBalance against it shows the curve fit is good — 0.29 / -0.02 / -0.001 / -0.07 dB — but that quality bought you a mono file.

Reach for match.applyMatchEq on the CLI when the deliverable is genuinely mono, such as a podcast or a voice track. For a stereo deliverable, either use a shape-matched solo processor through mastering-processor as above, or work through the library directly: mastering_pair_process() takes one flat array per call, so calling it once for the left channel against the reference's left channel and once for the right against the reference's right — the same way Reference Match's browser demo does it — gets you the fitted curve without discarding the channels. See the Python API for the call shape.

Step 6 — Confirm convergence

sonare mastering-pair-analyze tilted.wav --reference reference.wav \
  --analysis match.tonalBalance --json
# all four deviation_db values: 0.00

sonare mastering-pair-analyze tilted.wav --reference reference.wav \
  --analysis match.referenceLoudness --json
# {"gain_to_match_db": 0, "reference_lufs": -24.56, "source_lufs": -24.56}

The tonal correction closed the loudness gap too, on this file — but treat that as a property of this fixture, not a rule. reference.wav here differs from mix.wav by exactly one edit, an EQ tilt, and tilting the spectrum shifts measured LUFS along with it because the loudness curve is not flat across frequency; correcting the one edit undid both effects at once. In general, a tonal move and a loudness move are independent, and the honest sequence is: apply the tonal correction, then re-run match.referenceLoudness on the result — not on the untouched mix — because the tonal move itself will have shifted the number.

What Reference Matching Cannot Do

A matched curve moves tone, not decisions

Everything on this page adjusts EQ and gain. None of it touches arrangement, performance, or mix balance. If your chorus never lifts, if a doubled guitar buries the vocal, or if the arrangement is thinner than the reference's, a matched tonal curve will not fix any of it — it will just make the same thin, buried mix a little brighter. Reference Match puts it plainly: a reference calibrates, it does not transplant. If matching pulls a sparse track toward a dense one and it starts losing its own identity, the fix is to back off the match, not to push it further.

Where to go next

• Build the full chain this correction feeds into — Mix and Master a Song in the CLI.
• Turn the final loudness and true-peak numbers into a pass/fail gate — Gate a Delivery in CI.
• Read the decision rules behind every processor named here — Mastering Assistant and Mastering Processors.