This month a song came in for mastering as an MP3, and that was the only version that existed. The tool it was made in never offered a WAV. The artist asked a fair question: will this even work?
It does work. It just works inside limits, and you should know what they are before you pay anyone to master it.
What an MP3 has already done to your song
An MP3 saves space by throwing away the parts of the audio it guesses you won't miss. At high bitrates the guess is good. At low bitrates you start to hear it.
The top end gets cut off. Lower bitrate files often stop dead somewhere in the high frequencies. Air and shimmer above that line are simply gone.
Sharp sounds get smeared. Cymbals, hi-hats and consonants can pick up a swirly, watery edge.
Mastering makes all of it easier to hear. Mastering brings up level and detail. That includes the artifacts.
How to check what you actually have
Look at the bitrate. Open the file's properties. 320 kbps is the best an MP3 gets. At 128 kbps you're starting well behind.
Look at the top end. Drop the file into any free spectrum analyzer and look above 15 kHz. A hard flat ceiling means the encoder cut there. My note on the wall vs. the slope shows how to read it.
Don't convert it and call it a WAV. Saving an MP3 as a WAV makes the file bigger and changes nothing else. The missing audio stays missing. Send the MP3 as it is and tell me that's what it is.
Get the best version before you settle
Dig through the export settings. Some tools hide a higher quality download behind a menu or a paid tier. Check before you assume the MP3 is all there is.
Ask for stems. If the tool offers separate parts, they're sometimes cleaner than the full mix.
If the song is still early, think about where you finish it. If you're going to put real time and money into a track, starting from a tool that gives you a WAV saves you a ceiling later.
What mastering can still do
A lot. Balance the tone, set the loudness for streaming, tighten the low end and make it hold up on a phone and in the car. What it can't do is put back detail the MP3 threw away. I'd rather tell you that up front than have you hear it after release.
If an MP3 is all you've got and the song matters to you, send it. Just send it knowing what we're working with.
Josh, Founder, JG BeatsLab
Want this handled on your track? I master AI-generated music by hand, one song at a time, and every master comes with a Mastering Dossier that shows what I did and why. Book mastering or take the 3-minute scorecard to see where your workflow stands.
