SampleLab guide
What's Inside an MPC Sample .xpj File?
Updated September 2026
Every project you make on the Akai MPC Sample lives in a .xpj file. It's the thing you save to the SD card, the thing that holds your sequences, pads, and sample references. I spent months figuring out exactly how it works so SampleLab could read it directly. Here's what's inside.
A project is two things, not one
When you save a project on the MPC Sample, you get a .xpj file plus a companion folder (your ProjectData folder) holding the actual audio samples. The .xpj describes the music — sequences, notes, pad assignments, which sample each pad plays — while the folder holds the WAVs it points to.
This matters: if you copy a .xpj without its ProjectData folder, the project loads with missing samples. Always keep the two together.
Under the hood: compressed JSON
A .xpj file is gzip-compressed JSON with a small header. Uncompress it and you get a readable description of your project: the sequences and their note events, the programs and pad layouts, tempo, and the relative paths to each sample.
Nothing about it is encrypted or proprietary in the scary sense — it's just a format Akai never documented. Reading it correctly took months of testing against real projects: edge cases in timing, pad mappings, and sample references all had to match what the hardware actually does.
Why read it directly?
Because it means zero export steps and zero rebuilding. SampleLab opens the .xpj straight off your SD card — the same file your MPC Sample uses — and shows your sequences, notes, pads, and samples on your Mac.
There's no conversion, no intermediate format, no 'import' that might mangle your timing. What you see is your project.
Read-only, always
SampleLab never writes to your .xpj or your samples. It reads the project, lets you arrange, edit, and export, and leaves the originals exactly as they were.
That's a deliberate design choice: your MPC Sample project is the source of truth. The Mac is where you finish things, not where you risk them.
What you can do with it
Once open: arrange sequences into a full song, edit and nudge notes, swap or trim samples with waveform view, adjust gain and pan per pad — then export a stereo WAV, per-pad stems, or MIDI.
SampleLab is a Mac companion for the Akai MPC Sample, $14.99 one-time, for macOS 14 and later.
Made for MPC Sample owners who want to finish beats without a DAW. SampleLab is $14.99 one-time.
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