The Elektron Octatrack MKII is one of the most capable performance samplers ever made, and one of the most confusing to set up. The interface gives you very little hand-holding. The manual covers the front-panel side of things in detail but spends much less time on how samples get onto the card, what the folder structure actually means, and how to keep a library organized as it grows.
This guide covers all of that: the mental model the Octatrack uses for samples, the file-system layout on the CompactFlash card, how Flex and Static machines differ, the format requirements, and the workflow patterns that hold up once you have more than a few dozen samples to manage.
The mental model
Three concepts run through everything on the Octatrack: Sets, Projects, and Sample Slots. Get the hierarchy clear in your head before you touch the card, because every sample-related decision sits inside it.
A Set is a top-level folder on the CompactFlash card. It contains its own audio pool (the AUDIO/ folder) and any number of projects. The samples in a Set’s AUDIO pool are shared across every project inside that Set.
A Project is a sub-folder within a Set. It holds patterns, parts, arrangements, scenes, and references to samples assigned to slots. Projects within the same Set draw from the same audio pool. Projects in different Sets are completely independent.
A Sample Slot is an assignment inside a project. Each project has 128 Flex sample slots and 128 Static sample slots. Slots reference samples (either by loading them into RAM in the Flex case, or by streaming from the card in the Static case). Slots are where samples get a number that machines on the audio tracks can call.
This three-level structure is the source of most confusion. You can have a sample sitting in Set1/AUDIO/kicks/kick01.wav, but it doesn’t “exist” on the device in a musical sense until you assign it to a Flex or Static slot inside the current project. Browsing the card and assigning to a slot are two different operations.
What goes on the CompactFlash card
The Octatrack reads samples from a CompactFlash card formatted as FAT32. The card capacity is officially specified up to 64 GB; some users have reported larger cards working, but 64 GB is the safe limit.
A typical card layout looks like this:
CompactFlash Root/
├── MySet1/
│ ├── AUDIO/
│ │ ├── kicks/
│ │ │ ├── kick01.wav
│ │ │ └── kick02.wav
│ │ ├── snares/
│ │ ├── loops/
│ │ └── one-shots/
│ ├── Project1/
│ └── Project2/
├── MySet2/
│ ├── AUDIO/
│ └── (project folders)
└── (more Sets)A few rules worth knowing:
- Sets must be at the root of the card. The Octatrack will not see Sets nested inside other folders.
- The
AUDIO/folder is reserved. Don’t rename it, and don’t put anything other than audio files (and folders of audio files) inside. - Subfolders within
AUDIO/are browsable on the device. The Octatrack’s sample browser walks the folder tree, so organizing by category (kicks, snares, loops) is the natural way to keep things findable on hardware. - Project folders are managed by the Octatrack itself. You create them on the device, not on the computer.
The “everything outside AUDIO/ is left alone” rule matters. Some users have lost work by putting non-audio files inside a Set folder, or by reorganizing through a computer in ways the Octatrack didn’t expect. Stick to managing audio files in AUDIO/, and let the device manage everything else.
Sample format
The Octatrack accepts a narrow band of formats. Files outside this window won’t load.
- WAV only. No AIFF, no FLAC, no MP3.
- 44.1 kHz only. Files at 48 kHz or 96 kHz will not load, even though they’re valid WAV files. The Octatrack’s playback engine assumes 44.1 kHz throughout.
- 16-bit or 24-bit. 32-bit float is not supported.
- Mono or stereo. Both load fine.
If you’re coming from a workflow that produces 48 kHz files (most DAWs default to 48 kHz now), you’ll need a conversion step before files go on the card. There’s no on-device conversion: the Octatrack just refuses to load anything outside spec.
The other common gotcha is metadata. Some WAV files arrive with non-standard chunks that confuse the Octatrack’s parser. If you have a file that’s nominally the right format but won’t load, re-exporting it through a tool that writes clean WAV (Audacity, Reaper, ffmpeg, SampleStack) usually fixes it.
Flex vs Static machines
Each track on the Octatrack runs a machine. Five types matter for sample playback: Flex, Static, Thru, Neighbor, and Pickup. The two that touch sample management are Flex and Static.
A Flex machine plays back samples that have been loaded into the Octatrack’s 80 MB of RAM. Flex samples support the full real-time manipulation feature set: time-stretch, pitch-shift, slice playback, conditional triggers, parameter locks, the works. They’re called “flex” because they’re flexible.
A Static machine plays back samples streamed directly off the CompactFlash card. Static samples have a more limited feature set (no real-time time-stretch, for example) but don’t consume RAM. They’re how you play back long files: anything over a minute or two of stereo audio is better as a Static sample than a Flex one.
You get 128 Flex sample slots and 128 Static sample slots per project. The slots are where samples earn a number the machines reference. A Flex machine on Track 3 doesn’t directly “have” a sample; it references Flex sample slot 1 (or 2, or whatever you’ve assigned).
The practical split:
- Use Flex for one-shots, drum hits, short loops, and anything you want to time-stretch, slice, or manipulate live. RAM constraints mean you have to budget: 80 MB total, divided across however many Flex samples you want loaded.
- Use Static for long tracks, ambient beds, recorded performances, anything over a minute. The card streams them on demand, so memory isn’t a concern.
Most performances mix the two. A Static machine playing a 90-second drone bed, Flex machines on the other tracks doing the active sample work. The 80 MB RAM ceiling becomes a real constraint pretty quickly once you start working with full-length stereo files at 44.1 kHz, 24-bit (about 250 kB per second), so Static is the relief valve.
Transferring samples to the card
There are two ways to get samples onto the card:
Direct via card reader. Pull the CompactFlash card out of the Octatrack, plug it into a CF card reader, drag and drop files into SetName/AUDIO/ (or subfolders thereof), eject cleanly, put the card back. This is the fastest way to move large numbers of samples.
Via USB. The Octatrack supports USB mode for connecting the device directly to a computer. Hold FUNC and press SYSTEM, then navigate to USB DISK MODE. The card appears as a USB drive on your computer. Same drag-and-drop workflow, but no need to physically pull the card.
Either way, the files land in SetName/AUDIO/ (or a subfolder you’ve created). The Octatrack picks them up the next time you browse for samples in a project.
A few transfer rules to internalize:
- Eject cleanly. The Octatrack’s filesystem is FAT32, which is unforgiving about interrupted writes. Always use the OS’s eject or safely-remove option before pulling the card or disconnecting USB.
- Don’t transfer while the Octatrack is playing. Stop playback first.
- Avoid renaming files after they’re assigned to slots. The Octatrack references samples by file path, so renaming after assignment breaks the reference. If you need to rename, do it before slotting.
Sample slots: assigning, reusing, and replacing
Browsing samples on the card and assigning them to slots are two distinct operations. The browser (under SRC > PLAYBACK > SLOT) walks AUDIO/ and lets you pick a file, but the file isn’t “loaded” until you assign it to a slot.
A few patterns that come up:
- One sample, many slots. You can assign the same source file to multiple Flex slots with different settings (start point, end point, slice configuration, etc.). The source file is shared, but the slot parameters are independent.
- Slot reordering. Flex and Static slots have stable numbers, and patterns reference slots by number. If you reorder slots, patterns can suddenly play different samples. Reorder cautiously, or before patterns are written.
- Replacing a slot. Sometimes you want to keep all the slot parameters (slice points, start/end, etc.) but swap the source file. The Octatrack supports this directly: replacing a slot’s source file preserves the slot’s parameters.
The slot model is what makes the Octatrack a performance instrument rather than just a sampler. Slots are reusable references, and the parameters attached to a slot (slices, pitch, loop points) travel with the slot through every pattern that uses it.
Slicing and sample chains
Slicing is where the Octatrack really earns its reputation. A Flex sample can have up to 64 slices, defined either manually (drop slice points at specific times) or automatically (the Octatrack can attempt transient detection). Once sliced, individual slices can be triggered by step trigs, parameter locks, or via a slice grid that lets you sequence the slices like notes.
Sample chains are a related concept: a single WAV file containing multiple samples concatenated end-to-end, with slice points marking the boundaries. Sample chains are a memory optimization. Instead of using one Flex slot per drum hit (eating into your 80 MB RAM with file headers and small samples), you concatenate them into one file and slice it. One slot, many sounds.
Sample chains are most commonly used for drum kits. Concatenate eight drum hits into a single 4-second WAV file with slice points at the right positions, load it into a Flex slot, slice it, and you have a complete kit in one slot. The Octatrack has dedicated machine types for triggering specific slices, so this works musically as well as memory-wise.
This guide doesn’t go deep on sample chains because they deserve their own treatment. The short version: chains are how you fit a working drum kit into a Flex slot without burning eight separate slots on individual hits.
Common workflow problems
A few things catch nearly every new Octatrack user:
“My samples won’t load.” Almost always a format mismatch. Check the file is 44.1 kHz, 16 or 24-bit, mono or stereo WAV. The Octatrack doesn’t tell you why a file failed to load; it just refuses.
“The file is at the right sample rate but still won’t load.” Could be a non-standard WAV chunk. Re-export through a clean tool.
“My samples play at the wrong pitch.” Usually means the source file is 48 kHz but the Octatrack’s playing it as if it were 44.1 kHz. Resample to 44.1 kHz before transfer.
“My patterns are playing the wrong samples.” Slot numbers shifted, often because slots were reordered after patterns were written. Patterns reference slots by number, not by content.
“I’m running out of RAM.” Move long samples from Flex to Static, or use sample chains to fit more Flex content into fewer slots.
“The Octatrack froze during sample loading.” Almost always a card issue. Slow or incompatible CompactFlash cards struggle with the Octatrack’s read patterns. SanDisk Extreme cards have a reputation for working reliably. The Octatrack itself does fine; the card is usually what fails.
“I deleted a file from the card on my computer and now everything is broken.” Don’t do this with samples that are assigned to slots in active projects. The Octatrack stores the file path; deleting the file leaves the slot pointing at nothing. Clear the slot first, then delete.
A workflow that scales
Once you have a few hundred samples organized, a few habits help keep things manageable:
Use AUDIO subfolders aggressively. The Octatrack’s sample browser walks the tree, so kicks/, snares/, loops/, one-shots/, fx/, vocals/ (or whatever taxonomy works for you) makes finding things on-device fast. Without subfolders, you’re scrolling through a flat list.
Match sample prep to slot type. Files destined for Flex slots should be short and clean. Files for Static slots can be longer and don’t need to be loop-edited. The prep work for one isn’t the prep work for the other.
Use Sets to separate projects with shared source material. Sets sharing an AUDIO pool means one set of source files for everything in that Set, which is a big win when you’re developing a piece with consistent palette. New project on different material, new Set.
Cycle your samples. The 80 MB Flex RAM ceiling is real. Build a habit of clearing unused Flex slots regularly. Old projects accumulate slots that aren’t doing anything, and the RAM ceiling stops being conceptual the moment you can’t load the kick you want.
Back up the card. CompactFlash cards fail. Drag a copy of the card contents to a folder on your computer every so often. The Octatrack’s projects are just files in folders; restoring is a matter of putting them back.
Where SampleStack fits
Most of the work above happens once you’re at the device. The part that happens before, the prep step, is where files get into a state the Octatrack will accept.
For one or two files, manual conversion in your DAW is fine. Drop a file in Reaper, set the project rate to 44.1 kHz, export as 16-bit WAV. For a library of hundreds of samples coming from mixed sources at mixed rates, that workflow doesn’t scale. SampleStack reads your existing library in whatever format it’s in, validates every file against the Octatrack’s specs, converts what needs converting, and exports the right Set/AUDIO folder layout to your CompactFlash card.
For more on the format side, the compare formats guide has Octatrack alongside every other supported instrument. For the broader picture on file formats, WAV vs AIFF vs FLAC for hardware samplers covers the container differences in more depth. And the Octatrack instrument page has the full technical spec sheet.
The Octatrack rewards investment. The interface is famously unforgiving, but once the file-management side is sorted, you stop fighting the device and start playing it.