What Is Mastering?
Mastering is the last step before a record is released, after mixing is done. A mastering engineer takes a finished stereo mix, fixes any technical problems, makes small adjustments to how it sounds, and prepares the exact files each platform or format needs.
Mastering finalizes music by balancing art and science. Technical analysis supplies the data, and intuition and a deep connection to the music decide what to do with it.
Mastering has three parts:
How mastering works
Quality control. I hear the mix for the first time, in a room I trust. I have no history with the record. I wasn't there when the kick got compressed or when the vocal got pushed up on day nine. I hear what's there. That's how I catch clicks, pops, distortion, phase problems, and imbalances the mix room was hiding, like room modes. None of it is a mistake by the mix engineer. Audio sounds different in a different room, and mine is built to be accurate. I also check true peak and inter-sample peaks, dynamic range, crest factor, spectral balance, and stereo image, and compare against reference material. More on that in what QC involves.
Fine-tuning. Small moves. EQ for tonal balance, compression for cohesion, and a limiter set by what the music needs. The question behind every decision is whether it translates to other systems, other rooms, and other playback levels. If a mix is balanced and translating, I leave it alone. Knowing when to stop is part of the job.
Deliverable assembly. This part isn't creative. One miscoded ISRC or a PQ error can undo everything that came before it. Formats aren't interchangeable, and each has its own demands:
Streaming. A 24-bit WAV at the native sample rate, sequenced, trimmed, and checked against true peak and loudness targets. Apple Digital Masters adds encoding requirements and a certification process to confirm the file holds up through AAC conversion.
Vinyl. A separate pass, made with the cutting lathe in mind. Low end that works in digital can make a stylus skip or make a cut impossible, and sibilance that's fine on streaming becomes a problem on lacquer. A vinyl pre-master isn't the digital master with the level turned down.
CD. A 16-bit, 44.1kHz DDP 2.0 image with track markers, ISRCs, PQ data, gaps, and sample-accurate edits. Dither goes on here, not before. Errors surface at the replication plant, and fixing one after manufacturing starts is an expensive way to learn what a PQ code is.
Hi-res digital. Delivered at the session's native sample rate, 24-bit, typically 88.2kHz or higher. If it was converted upstream and converted back, it isn't hi-res anymore.
Cassette. Cassette has limited high-frequency response, a higher noise floor, and a bias that varies between tape stocks. It usually needs its own master, with extra care around harsh highs, sibilance, and how hard the limiter is working. If someone is pressing cassettes, they care about the format, and the master should reflect that.
Mastering vs. Automated Tools
Automated tools can adjust level and tonal balance. They can't listen. They won't hear that the chorus feels smaller than it should, that the low end is masking the kick on a phone speaker, or that the dynamic contrast in the bridge is the best thing on the record and should be left alone. That takes judgment about what the music is doing and where people will hear it, and I've built mine over years of working with real rooms, formats, and records.
What is the difference between mixing and mastering?
Mixing happens inside the session. The mix engineer balances the tracks, shapes each instrument, places sounds in the stereo field, and hands over a stereo file.
Mastering starts from that file. I never open the mix session, so there are no faders and no way to pull up the snare. I get the stereo mix and hear it fresh, in a different room, on a different system. That distance is the point. Someone who has lived inside a record for weeks can't hear it the way a listener will. I can.
What do I send to a mastering engineer?
A stereo WAV or AIFF at your session's native sample rate, 24-bit minimum (32-bit float is ideal), with peaks below 0 dBFS. No dithering and no sample rate conversion before sending. The longer version depends on your formats and whether you're working from tape. See Mix Preparation and File Delivery for Mastering.
Loudness, dynamics, and LUFS
Streaming platforms normalize loudness. A master pushed hard against the ceiling gets turned down and doesn't get its dynamics back, which leaves it flat and tiring at a lower level. A master that keeps its dynamics and headroom benefits from normalization instead of just surviving it.
The integrated LUFS number tells you the average level, not whether it sounds good. Short-term loudness, crest factor, and true peak all affect how a master behaves on a given platform. For platform-by-platform targets, see Mastering Loudness Targets for Streaming.
Common questions
Do I need mastering? If the record is being released, yes. Streaming, vinyl, CD, and label submission each have format-specific requirements, and fresh ears in an accurate room catch things that pile up unnoticed over a long mix. Nothing is better than being more done.
What does mastering do? Quality control to catch errors, fine-tuning to optimize the audio, and deliverable assembly to prepare the files each format needs.
What does a mastering engineer do? Listens critically in an accurate room, makes small adjustments to level, tone, and dynamics, and assembles the final deliverables.
What is the difference between mixing and mastering? Mixing works inside the session with individual tracks. Mastering works with the finished stereo mix and prepares it for release. Separate jobs, separate rooms, separate ears.
How long does mastering take? A single or EP is typically five to seven business days from file delivery. An album takes two to four weeks depending on length and complexity. Rush turnaround is available, and a strong mix keeps revisions from adding time.
How much does mastering cost? It depends on the project. Get in touch and I'll give you a specific number.
Can mastering fix a bad mix? Not fundamentally. It can improve clarity, balance, and translation, but it can't replace decisions that belong in the session. If the mix has a real problem, go back and fix it first.
What is stem mastering? It uses grouped submixes (drums, bass, vocals, and so on) instead of one stereo file, which allows more targeted processing. The tradeoff is that it blurs the line between mastering and mixing. Part of a mastering engineer's value is never having touched the session, and stems close that distance.
