Your mix is finished and it needs mastering. One option takes minutes: upload the file to an automated online mastering service and download the result. The other takes a few days and a conversation: send the mix to a mastering engineer. Both can work. Which one to choose depends on the song, the release and how confident you are in your mix.
What automated online mastering does
An online mastering service analyses your mix and applies a chain of processing chosen by software. Usually that means some EQ, compression, stereo adjustment and a limiter to reach a target loudness. Many services let you choose a style or intensity and compare versions before you download.
The strengths are real. It's fast, it's available at three in the morning, results are consistent, it usually costs less than an engineer's time, and you can try several settings in an evening.
The limits are real too. The software processes what it hears, and it doesn't ask questions. It can't tell a deliberately quiet intro from a mistake. It won't fix a problem in the mix, only make it louder. With dynamic music it can push the limiter too hard. And it will never tell you that your vocal sits too far forward and the mix needs another look.
What a mastering engineer adds
A mastering engineer is a second pair of trained ears, usually in a room and on speakers built for this job. What you're paying for is mostly judgement.
- Knowing when to do less. Sometimes the best master changes very little.
- Feedback on the mix. A good engineer may ask you to fix something and resend, which no algorithm does.
- Consistency across a release. On an EP or album, songs need to sit together in level and tone, with the right gaps between them.
- Catching problems. Clicks, distortion, noise before the first note, a reverb tail cut too early.
- The right deliverables. A master for streaming, plus other versions or formats if you need them.
When online mastering makes sense
- Demos, pitches and songs you're sending around for feedback.
- Quick singles in a genre with a clear modern sound, when you know your references well.
- When your mix is careful and you've compared several settings at matched volume.
- As a learning tool. Hearing what processing does to your mix teaches you a lot about mixing.
When an engineer is worth it
- EPs and albums, where songs have to belong together.
- Dynamic and acoustic music: jazz, classical, folk, singer-songwriter, traditional music. Heavy automatic limiting can flatten exactly what makes these recordings breathe.
- Releases you're investing in, with a video, promotion and pitching planned around them.
- When you're unsure about your mix or your room. If you mixed only on headphones or in an untreated room, an outside ear is worth more.
A made-up artist, Mara Vale, does both. She runs demos through an online service before sending them to collaborators. For her EP, she books an engineer and sends five mixes, a reference track and a short note for each song.
Preparing your mix for either
Most problems with masters start in the mix file. Prepare it the same way whichever route you choose:
- Leave headroom. Nothing should clip on the master bus. Keep peaks a few decibels below zero.
- Bypass your own limiter. Remove loudness processing from the master bus, or tell the engineer it's there and why.
- Export a WAV at the session's sample rate, in 24-bit or 32-bit float. Never send an MP3.
- Keep the edges. Leave a short moment of silence at the start and let reverb tails ring out at the end.
- Check before sending. Listen in mono and on a couple of different speakers.
- For an engineer, add context: one or two reference tracks, a note about what you love in the mix and what worries you, and for an EP the song order. Name files clearly, like "Artist - Title - Mix v3".
Whatever route you take, keep the final master as a high-quality WAV. Distributors, including CULT, ask for WAV files.
How to judge the result
- Match levels before comparing. Louder almost always sounds better at first. Turn the master down to the level of the mix, then decide.
- Listen on everyday devices: phone speaker, earbuds, car, laptop.
- Compare with your own mix, not just with references. Did anything you loved disappear, such as warmth in the vocal or punch in the drums?
- Check the details. The loudest section for distortion, the start and end for clicks or cut-off tails.
- Remember normalisation. Most major platforms adjust playback loudness, so a master that's pushed much louder won't play louder. It will only lose dynamics.
Plenty of artists end up with a mix of both: online mastering for drafts and quick releases, an engineer for the songs that matter most.