If you have ever sent a mix out for mastering and gotten an email back asking for a different export, a version without limiting, or a corrected sample rate, you already know the problem. Knowing what files to send to mastering engineer is not a minor detail. It directly affects how much can be improved, how fast the session moves, and whether your final master sounds polished or boxed in.
A strong master starts with the right source file. The cleaner and more intentional your delivery is, the more your mastering engineer can focus on tone, depth, punch, translation, and format preparation instead of fixing preventable issues.
What files to send to mastering engineer first
For most projects, the main file to send is a stereo mix export in WAV or AIFF format. That file should be the full-resolution version of your final mix, exported directly from your session without MP3 conversion, without sample-rate changes for convenience, and without unnecessary processing on the mix bus.
In practical terms, that usually means a 24-bit or 32-bit float stereo WAV at the session's native sample rate. If your mix was created at 44.1 kHz, send 44.1 kHz. If it was created at 48 kHz or 96 kHz, send that. Do not upsample a 44.1 kHz session to 96 kHz just because it looks more impressive on paper. Upsampling does not create new detail, and it can complicate quality control.
If your engineer accepts AIFF, that is also fine. WAV is simply the most common delivery format because it is widely compatible and dependable across DAWs and mastering systems.
The best export settings for mastering
The safest move is to export your final mix as a stereo interleaved file with no dithering unless you are specifically asked for it. Dither is generally applied at the final bit-depth reduction stage, which is often part of mastering delivery, not mix export.
Leave some headroom, but do not get obsessive about a specific number. A mix peaking around -3 dBFS to -6 dBFS is usually comfortable. What matters more is that the mix is not clipped, flattened, or crushed by a limiter on the stereo bus.
If you love the sound of your bus compressor and it is part of the mix, that can stay. If you have a limiter only to make the mix louder for reference playback, remove it before export. Loudness can be added in mastering. Lost punch and distortion usually cannot be removed cleanly.
Should you send a limited version too?
Sometimes, yes. The main file should still be the unlimited master-prep mix, but sending a second reference version with your mix bus processing can be helpful. It tells the engineer what you have been hearing and what level of aggression or density you were aiming for.
That reference is not the file to master from unless you specifically agree otherwise. It is a guide.
What not to send
A surprising amount of mastering delay comes from file issues that have nothing to do with the music itself. MP3s are the most common mistake. They are fine for approvals and texting a rough to your bandmate, but not for mastering source.
Avoid sending files with clipping on the print, fade-outs you are not sure about, sample-rate converted versions made after the fact, or mixes printed through stereo enhancement plugins that you have not checked in mono. Also avoid exporting from a session with processing on the master bus that you forgot was there. That happens more than people admit.
If your mix is already heavily limited because you were chasing commercial loudness, mastering becomes more about damage control than enhancement. The engineer may still improve it, but your options get narrower.
If you are sending stems instead of a stereo mix
Stem mastering can be extremely useful, but only when it is intentional. If your engineer requests stems, send clearly labeled stereo stems that all start at the exact same timecode and run the full song length. Typical stem groups might include drums, bass, music, lead vocal, and background vocals, though the exact breakdown depends on the song.
Do not send random groups with overlapping bus processing unless there is a reason. And do not send stems plus a stereo mix that does not null against them unless you explain why. Consistency matters.
Stem mastering offers more control, especially when a mix is close but not quite translating. Still, it is not a replacement for finishing the mix. If your vocal balance changes every chorus or your low end is fighting itself, that is usually a mixing issue first.
Label everything clearly
File names should be simple and readable. SongTitle_FinalMix_24bit_48k.wav is useful. finalFINAL2_REAL.wav is not. If you are sending multiple versions, label them with purpose, such as Main Mix, Instrumental, Clean, TV Track, or Vocal Up 1 dB.
This sounds basic, but good labeling prevents mistakes during sequencing, approval, and final delivery.
Include reference notes, not a novel
The audio file is the priority, but notes matter. If there is a specific concern, say it plainly. Maybe the vocal feels a touch sharp on earbuds. Maybe the kick and bass relationship is right in the studio but weak in the car. Maybe you need the project prepared for streaming, CD/DDP, Apple Digital Masters, vinyl pre-mastering, or high-resolution delivery.
That information helps the engineer make decisions that fit your release path.
What is less helpful is a page of vague adjectives with no hierarchy. Warm, huge, modern, vintage, open, aggressive, natural, expensive - those can all point in different directions. If you send reference tracks, explain what you mean by them. Is it the low-end weight, the vocal size, the top-end smoothness, or the overall loudness?
Common questions about what files to send to mastering engineer
One of the biggest questions is whether to include mix bus EQ or compression. If it is genuinely part of the sound, leave it in. If you are unsure, send two versions - one with the processing and one without - and say which one reflects your intent.
Another question is whether to normalize the file. No. Leave normalization off. It does not improve quality, and it can interfere with predictable gain staging.
People also ask about 16-bit exports. Unless the engineer specifically requests 16-bit, send the higher-resolution source file. Bit-depth reduction is usually handled at the final delivery stage.
And yes, you should listen to the export before sending it. Start to finish. Not just the first chorus. You are checking for clicks, missing automation, cutoff reverbs, wrong fades, and export glitches. That five-minute check can save a day of back-and-forth.
A simple delivery checklist that actually helps
Before you upload anything, make sure you are sending the final approved mix, exported as a stereo WAV or AIFF at the native session sample rate and high bit depth, with no clipping and no loudness limiter unless it is intentionally part of the sound. Include clear file names, any alternate versions you actually need, and a short note about goals and delivery format.
If your project needs manufacturing or platform-specific assets, say so up front. A song headed to streaming only has different practical needs than an album requiring DDP, sequence spacing, ISRC entry, CD-Text, or a vinyl pre-master.
At LB-Mastering Studios, this is exactly why the process starts with file evaluation and direct communication. Good mastering gets better when the handoff is clean.
The goal is not just sending a file
The real goal is giving your mastering engineer the best possible version of your mix, with enough context to finish the record properly and no technical baggage that gets in the way. That means clean exports, honest headroom, clear labeling, and a short note that explains what the release actually needs.
When that part is handled well, mastering becomes what it should be - the final quality-control checkpoint and sonic finish that helps your music translate everywhere people hear it. If you are not sure whether your mix is ready, ask before you export. That one question is often the difference between a quick, confident approval and a revision cycle you never needed.
