Sample slicer

How the chopping works

Drop a file and it is cut at every hit straight away. To find the hits, the sound is split into 24 bands from the kick's thump to the hi-hat's fizz. The page then looks, 86 times a second, for moments when a band suddenly gets louder. A band-by-band view matters. Counting every frequency the same way, a kick hides under the noise of the cymbals, and in an early version a kick at full level was missed for exactly that reason. A hit has to stand out from the last third of a second around it, not from the whole file, so quiet ghost notes in a busy break still count.

Finding a hit is half of it. The other half is where to cut, because a slice that starts a few milliseconds late has lost the snap that made the sound worth sampling. Each hit is traced back through a fine envelope, 0.7 millisecond windows, to the steepest part of its attack. The cut goes a millisecond and a half before that, then back to the nearest point where the waveform crosses zero. Every slice also gets a tiny fade at each end. Hardware samplers play a slice from its first sample, and one that starts or ends mid-wave clicks.

What was measured

The slicer is checked on every release against eight synthesized breaks, 211 hits in all. They mix kicks, snares, closed hats, claps and rims at levels from full down to −24 dB, some only 60 ms apart, over a reverb tail and a noise floor. At the default sensitivity it cut 91.9% of the hits, and every one of those cuts was no more than 3 ms before its hit and never late enough to clip the attack. 1.5% of cuts were not hits. Nearly all the misses are quiet hits landing 60 ms after a loud one, while the loud one is still ringing. If you need those, raise the sensitivity or click the waveform to add the cut. A sustained chord fading in from silence is cut where it begins and nowhere after, and every slice starts and ends on exactly zero.

Four ways to slice

• At the hits: for breaks and drum loops. Slide the sensitivity left for fewer, stronger slices (kick and snare only) and right to catch ghost notes.
• Into equal parts: 4, 8, 16 or 32. For a loop that is already exactly a whole number of bars, sixteen equal slices are sixteenth notes of one bar, or quarters of four. This is the classic way to rearrange a break.
• On the beat: every eighth, beat, half bar or bar at the tempo, which is detected when the file loads. The same detector powers the BPM finder. Check it; if the loop does not start exactly on a downbeat, trim it first with the cutter.
• By hand: click anywhere on the waveform to add a cut (it snaps to a zero crossing) and click a cut to remove it. Editing any of the other modes switches to this one, so your changes stay.

Playing the pads

Each slice is a pad. Tap it, or play it from the keyboard: the number row is pads 1 to 10, then Q to P, A to L and Z onward. Playing a pad stops the one before, like a choke group on a sampler, so you can finger-drum the slices into a new pattern and hear straight away whether the chop works before downloading anything.

Getting slices onto an SP-404 or MPC

The download is a zip of 16-bit PCM WAVs, numbered in order. The SP-404 MK2 and the TR-8S want 48 kHz. The original SP-404 and SP-404SX, and Akai MPCs, want 44.1 kHz. The sampler format page explains why a file in the wrong format loads silently or not at all. Mono is on by default: drum hits rarely need stereo, and mono halves the memory each pad uses. On an SP-404 MK2, copy the WAVs into the IMPORT folder on the SD card and import them from the pad's menu. On an MPC, drag the folder in and use it as a program. In a DAW, drop them on a drum rack or sampler track, one per pad, in order.

Where the samples come from

For a vocal chop or an isolated drum part from a full song, split it first with the stem splitter, then slice the stem. The audio editor can arrange slices back into a pattern on a bar grid with a metronome. And if the original is in the wrong key for your track, the key finder and the key changer fix that before you chop.