You open the folder. Sixty-seven files. No labels. Three different sample rates. Half of them are MP3s. There is a subfolder called “FINAL USE THESE” and another called “ACTUALLY USE THESE ONES.” A text file says “the vocal is in the other folder I sent last week.”
This is not mixing. This is archaeology.
Every freelance mix engineer has a session prep horror story. The producer who sends stems with mix bus compression baked in. The rapper who exports the beat as a single stereo file and expects you to mix individual elements. The band that sends a Pro Tools session from a version of Pro Tools you do not own.
Bad session prep is the silent tax on every mixing business. You do not bill for it. You do not talk about it. You just absorb it. And the hours add up fast.
Here is how to stop that.
Why Session Prep Problems Happen in the First Place
Most clients are not trying to make your life difficult. They simply do not know what you need. They have never been told how to export stems properly. They recorded in GarageBand and have no idea what “consolidated WAVs from the session start” means.
The responsibility falls on you. Not because it is fair, but because you are the professional in this exchange. A plumber does not blame the homeowner for not knowing pipe gauges. A mix engineer should not blame the artist for not knowing export protocols.
The fix is not complaining about bad files. The fix is telling clients exactly what to send before they send it.
The File Requirements Every Mix Engineer Should Set
Your session prep requirements should be a short, clear document you send to every client before they export a single file. Keep it under one page. Here is what it needs to cover.
Audio Format and Resolution
All files must be WAV format. Not MP3, not AIFF, not FLAC. WAV. At the same sample rate and bit depth the session was recorded in. If they recorded at 48kHz/24-bit, you want 48kHz/24-bit WAVs. Do not let clients convert sample rates themselves. That is where artifacts and quality loss creep in.
File Consolidation
Every audio file must start at the same point, usually the very beginning of the session or one bar before the song starts. This means if a guitar part only plays in the chorus, the WAV file still begins at bar one with silence until the guitar enters.
Without consolidation, tracks will not line up when you import them. You will spend twenty minutes aligning files by ear instead of mixing. That is unpaid labor you signed up for by not setting this requirement.
Most DAWs make consolidation simple. In Pro Tools, it is “Consolidate Clip.” In Logic, “Bounce Regions in Place.” In Ableton, “Consolidate.” Walk your client through the process for their specific DAW if they are unsure. A two-sentence explanation now saves you twenty minutes of alignment later. Some engineers include a short video walkthrough with their file requirements document. It takes five minutes to record and prevents the same question from coming up with every new client.
Track Labeling
Every file needs a clear, descriptive name. “Lead Vocal,” not “Audio_Track_23_bounce.” “Kick In,” not “drums_thing.wav.”
Suggest a naming convention. Something like: SongName_Instrument_Detail. So “Neon_LeadVocal_Main” and “Neon_BGVox_Chorus_High.” When the session has 80 tracks and they are all clearly labeled, you save yourself the guessing game of figuring out what “synth_pad_JEFF_v2_USE” is supposed to be.
Track count matters here too. Ask your client how many tracks are in the session before they export. If you quoted a mix based on “about 30 tracks” and 95 files show up, that changes the scope of the project. Knowing the count upfront lets you adjust your quote or set expectations about turnaround time before the files even arrive.
No Mix Bus Processing
Unless you specifically discussed it, all files should be exported dry. No compression, EQ, or limiting on the master bus. No “mastering chain” left on by accident. If the client wants to send a reference bounce with their mix bus chain for vibe reference, that is fine. But the individual tracks need to be clean.
This also applies to individual track processing. If the producer has an 1176 on the vocal that is essential to the sound, ask them to send two versions: one with the processing and one without. That gives you options without guessing whether the squashed dynamic range was intentional or accidental.
Reference Materials
Ask for a rough mix. Always. Even if it sounds terrible, the rough mix tells you what the client is hearing in their head. Without it, you are guessing at their intent.
A list of two or three reference tracks from other artists is also incredibly helpful. “I want it to sound like this” is more useful than paragraphs of written feedback. Reference tracks give you a target for tonal balance, vocal placement, and overall energy.
Be specific about what you want from the references. Ask the client to note what they like about each one. “I love the drum sound on this track” or “the vocal sits like this in the verse” is far more actionable than “I want my song to sound like Drake.” When clients pinpoint specific elements they are drawn to, you can match that intent without guessing.
Session Notes
Any information the client has about the session belongs in a short document or email. BPM. Key. Which vocal take to use. Whether the doubled guitars are meant to be hard-panned or stacked center. Any creative decisions that were already made during tracking.
You should not have to guess whether the three kick drum tracks are supposed to be layered or whether only one is the keeper. Session notes answer these questions in thirty seconds instead of thirty minutes.
Also ask about anything unusual. Did they record through hardware that adds character? Are there intentional distortion or lo-fi elements that should stay? Is the tempo consistent or does the song have tempo changes? These details feel minor, but discovering them mid-mix costs you time and concentration.
How to Actually Enforce Your Session Prep Requirements
Having a checklist is step one. Getting clients to follow it is step two.
Send the requirements document the moment a project is confirmed. Not when you are ready to start mixing. Not as an afterthought. Make it part of your onboarding process, right alongside the contract and payment terms.
Frame it as something that benefits the client. “Following these guidelines means I can start mixing faster and deliver your first mix sooner.” Nobody argues with getting their music back quicker.
When files arrive that do not meet the requirements, send them back. Politely, but firmly. “Hey, a few of these files are MP3s and they’re not consolidated. Can you re-export as WAVs starting from bar one? Here’s the guide I sent over.” This feels uncomfortable the first time you do it. After that, it becomes routine.
The alternative is worse. You accept the bad files, spend an hour fixing them, and then the client has no idea anything was wrong. Next time they send the same mess. You have trained them to keep doing it because it worked.
Think of it this way: a client who follows your session prep guidelines gets their mix back faster and with fewer revision rounds, because you spent your time mixing instead of organizing. That is a direct benefit to them. When you frame it that way, most clients are happy to follow the process.
If you charge for session prep work, make that clear upfront. “If files arrive outside of spec and I need to clean up, edit, or reorganize the session before mixing, that is billed at my hourly rate.” Some engineers include one hour of prep in their flat mix rate. Others bill it separately. Either approach works as long as the client knows before they send files.
The Real Cost of Skipping Session Prep Standards
Here is the math most engineers never do.
If you spend an average of 45 minutes organizing and troubleshooting messy sessions, and you mix four songs per week, that is three hours of unpaid work every week. Over a year, that adds up to more than 150 hours. At a modest rate of $50 per hour, you are giving away $7,500 annually by not having a session prep document.
That number gets worse when bad files cause actual mix problems. You mix a track, send it to the client, and they say “the vocal sounds weird.” You dig in and realize the stem was exported with a high-pass filter baked in at 200Hz. Now you are re-requesting files and re-mixing. That revision was not a creative decision. It was a technical failure that proper session prep would have prevented.
Multiply that across a full year of projects and the cost is staggering. Time you could have spent mixing. Time you could have spent finding new clients. Time you could have spent on literally anything besides sorting mislabeled audio files.
When Clients Cannot Meet Your Session Prep Standards
Not every client has the technical knowledge to export stems properly. Some are working in stripped-down DAWs. Some recorded on their phone. Some hired a producer who bounced everything and disappeared.
You have two options. First, you can offer session prep as a paid service. “Send me whatever you have, and I will organize and prepare the session for mixing at my hourly rate.” This turns a frustration into a revenue stream. Some engineers charge a flat session prep fee per song. Others bill hourly for anything beyond a clean, properly exported session.
Second, you can create simple export tutorials for the most common DAWs your clients use. A three-minute screen recording showing how to consolidate and export in Logic, Ableton, or FL Studio saves both of you time. Record it once, send it to every new client. Update it when the software changes. This is a small investment that pays off across dozens of projects.
The goal is not to turn away clients who do not know how to export properly. The goal is to build a process that gets the files right before they reach your inbox, so you can spend your time doing what you are actually good at: mixing.
Your Session Prep Checklist in One Place
Here is the short version you can copy and send to clients: WAV files only, same sample rate as the recording, consolidated from bar one, clearly labeled, no mix bus processing, rough mix included, and session notes with BPM, key, and creative decisions. That is the whole list. Print it, email it, pin it to your booking workflow.
Tools That Make Session Prep Easier
For the file transfer itself, the tool matters. Generic file-sharing platforms like WeTransfer or Google Drive accept anything. There is no structure, no labeling enforcement, no organization. You get whatever the client throws in the folder.
session.trackbloom.com handles this differently. When you send your client a dedicated upload link, their tracks arrive grouped by instrument type. Vocals in one group, drums in another, keys, guitars, bass, all sorted before you touch them. It is like WeTransfer built for audio, and it eliminates the most time-consuming part of session prep: figuring out what everything is.
Session Prep Is a Business Decision, Not a Technical One
Engineers tend to think of session prep as a technical problem. It is not. It is a business problem.
Every minute you spend organizing files is a minute you are not mixing. Every session you troubleshoot for free is margin you are giving away. Every time you accept messy stems without pushback, you are training that client to keep sending messy stems.
Setting clear file requirements is not being difficult. It is being professional. The best engineers in the industry all have some version of this process. They send specifications. They enforce standards. They protect their time.
You should too. Write the checklist. Send it early. Follow up when files do not meet the standard. Your mixes will be better, your turnaround will be faster, and your clients will respect the process because it makes their music sound better too.
That is a win for everyone.