What Is Audio Mastering? What It Does to a Song

Audio mastering is the last step between a finished mix and a release. It shapes the tone, holds the dynamics together, sets the stereo image and brings the song to the right loudness for where it will play. Here is what that means in numbers.

Mastering in one paragraph

A mix balances many tracks against each other. Mastering takes the finished stereo file as one piece and prepares it to be heard anywhere: on earbuds, in a car, on a club system, on Spotify next to other songs. A good master sounds like your mix, only finished. It is small moves, measured carefully.

What mastering changes, step by step

Step	What changes	Typical size of the move
Tone (EQ)	The balance of lows, mids and highs across the whole song	1 to 3 dB, wide shapes
Dynamics (compression)	How much the loud and quiet parts differ, and how glued the mix feels	1 to 2 dB of gain reduction
Multiband	One range held steady when it jumps, like a booming bass note	A few dB, only in that band
Stereo	Width above the bass, mono in the low end	Bass mono below about 140 Hz
Loudness (limiting)	The final level, in integrated LUFS	To about −14 to −8 LUFS, by genre
True peak	The highest point of the real waveform, between samples	At or below −1 dBTP for streaming

Then delivery: the right file (usually a 24-bit WAV), the right sample rate, metadata, and for an album the same tone and a planned loudness from song to song.

What real mixes look like before mastering

We measured 3,082 mixes people dropped into OBRA between 18 and 26 October 2026 (loudness only, no audio kept). They show why mastering is mostly about density and peaks, not just volume.

−14 LUFSmedian loudness of a mix before mastering
−16 to −11LUFS range of the middle half of the mixes
13 dBmedian peak-to-loudness ratio (PLR)
10.1 %of mixes quieter than −20 LUFS, far below streaming level

How loud is independent music in 2026?: the full study, method and CSV

Mastering vs mixing

	Mixing	Mastering
Works on	Every track: vocals, drums, bass, the rest	One stereo file
Fixes	Balance, a buried vocal, a kick against the bass	Overall tone, glue, width, loudness, peaks
Order	First	Last, after the mix is approved
Moves	Large, per track	Small, on the whole song

If the vocal is buried, mastering cannot dig it out without changing everything else. That belongs to the mix.

Mixing vs mastering: the full guide
Mix and master a vocal over a beat: free to listen

Ways to get a song mastered

Do it yourself in your DAW, with an EQ, a compressor, a true-peak limiter and a LUFS meter. Free, and it takes practice.
Use an automatic service. Seconds, and free or a few dollars. Good for demos, singles and fast releases.
Hire a mastering engineer. Days, and usually about $50 to $200 a song. Worth it for a record that matters a lot.

Free mastering course: 8 lessons to do it yourself
Online mastering services: what each kind costs and gives back
AI mastering: how automatic mastering works

Master a song free with OBRA

OBRA Audio Mastering runs every step above in your browser, so your file is never uploaded. It explains each move with its number and gives you three masters at the same loudness: Natural, OBRA and Loud.

2 different songs a day free, with no account: all three masters, the Studio and every meter, as a WAV or FLAC up to 24-bit / 48 kHz. Each extra song is a one-off $3 / €3 / £3 (unlimited downloads of that song for 30 days, 88.2 / 96 kHz and 32-bit float included), or unlimited with OBRA PRO, $10 / €10 / £10 a month.

Master your song free →

If the mix itself needs work, a person can help where a master cannot. OBRA ULTRA is mixing and mastering by an OBRA engineer: you send your tracks and get a WAV and a written note back, $19 / €19 / £19 per round, within 72 hours. Spots are limited each week.

Frequently asked questions

What is audio mastering in simple words?

It is the final polish of a finished mix: small changes to tone, dynamics, width and loudness so the song sounds finished and plays well on every system and service.

Is mastering just making a song louder?

No. Loudness is one step. Streaming services turn louder songs down anyway, so a good master balances tone and dynamics first and sets the level for where the song will play.

Does every song need mastering?

Every released song is mastered in some way, even if only by a limiter. Without it, a song usually sounds quieter, thinner or less even next to others in a playlist.

How long does audio mastering take?

Automatic mastering takes seconds. An engineer usually needs from a day to a week, depending on revisions and the queue.

Can mastering fix a bad mix?

It can soften small problems, like a slightly dark tone or a mix that is a little narrow. It cannot fix balance problems such as a buried vocal. Those belong to the mix.

What format should a master be?

Usually a 24-bit WAV at 44.1 or 48 kHz, with true peaks at or below −1 dBTP for streaming. Some stores also accept higher sample rates, like 88.2 or 96 kHz.

What is audio mastering? What it does to your song