A sample chain is one WAV holding many sounds end to end, sliced on playback. On the Octatrack it is not a convenience — it is how you fit a set on the machine at all. The OT has 128 sample slots per project and a finite amount of Flex RAM; eight kicks as eight files cost eight slots, and as one chain they cost one.

Everyone works this out in their first week. What takes longer is working out why chains built the obvious way sound wrong.

The rule everything follows from

The Octatrack's fast slicing divides a sample into N equal parts.

That is the whole problem. A kick is 400 ms. A crash is three seconds. A vocal chop is whatever it is. Concatenate eight of those back to back and the file is unevenly divided by construction, so when the machine cuts it into eight equal pieces, the boundaries land wherever they land — in the middle of the crash, halfway through the third hit, and your trigs play the tail of one sound and the front of the next.

The chain is not "slightly off". It is unusable, and it is unusable in a way that sounds like the machine's fault.

The fix: pad every slot to the longest

Do not write the hits end to end. Decide the slot length first:

slotFrames = max(length of every hit in the chain)
slot i starts at i × slotFrames

Each hit is written at the start of its slot, and the rest of the slot is silence. The file is now exactly N equal parts long, so the machine's equal division lands precisely on the first frame of every hit. Every time, with no metadata at all.

The cost is file size and RAM. A chain of eight hits where one is a three-second crash is 24 seconds long regardless of how short the other seven are. That is the trade, and it is almost always worth it — but it is why you do not want one long ride cymbal in a chain of otherwise short drums. Put the long sounds in their own chain.

A useful number to watch while building: the padded length in seconds, which is what determines the Flex RAM the chain will occupy. If padding is doubling your chain, you have one outlier in there.

Then add the `.ot` anyway

The padding makes the chain work with no metadata. A .ot file alongside it makes the chain sample-accurate: it carries the exact, unpadded slice points, so the machine jumps to the real start of each hit and stops where the audio actually ends rather than playing out the silence.

These are complementary, not alternatives:

Padding only — works anywhere, including on someone else's machine and in any other sampler that does even slicing. Plays the trailing silence.
.ot only — sample-accurate, but if the file is ever resliced on the machine, or the .ot is lost in a rename, the chain falls apart.
Both — degrades gracefully. This is what you want.

The .ot format is documented field by field in How Octatrack .ot slice files actually work.

The rest of the build

Sample rate. 44.1 kHz. The OT resamples anything else on load, which is a quality hit you took for no reason. Convert before you build the chain, not after.

Bit depth. 16-bit is the machine's engine and half the card space; 24-bit is there if you want the quantising step gone. 16-bit is the right default for a chain of drums.

Stereo. Keep it if the source is stereo. Chains of mono drums should stay mono — it halves the RAM for no audible loss.

Level. Limit, never normalise. Normalising each hit to peak destroys the relative balance you chose when you picked those sounds together; normalising the whole chain up does the same thing more subtly. If the sum would clip, pull it down.

Slice count. Multiples of 8 — 8, 16, 32, 64 — because that is how the trigs lay out under your fingers. 64 is the ceiling the .ot format allows.

Order. Put the sounds in the order you will play them, not alphabetically. You are building an instrument, and the trig row is its keyboard.

Naming, so you can find it in six months

The machine shows you a short name in a list, on a small screen, in a dark room. Put the facts in it:

KICK-DIST-8-120.wav
BASS-Fm-16-120.wav
808-KIT-16.wav

Content, count, and tempo if it is tempo-dependent. Anything that makes you open the file to remember what it is has failed.

A checklist

Pick sounds that belong together and are of similar length.
Convert everything to 44.1 kHz first.
Find the longest; that is the slot length.
Write each hit at the start of its slot, pad the rest with silence.
Limit if it clips. Do not normalise.
Write the .ot with the real, unpadded slice points.
Name it so the OT's screen tells you what it is.

WeaveTone does all seven from a typed prompt — "a distorted kick chain of 8", "a bass chain in F minor" — against your own library, and shows you the padded slot length before you export. See what it does or get the macOS build.

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