Field Sampler — interface walkthrough

1First launch0.5 s

The app opens on a blank session: no dialogs, a prompt to record or import, and every control in place.

• ✓Empty-state prompt shown
• ✓Fits the screen without scrolling
  overflow 0 px wide, 0 px tall
• ✓Pads and keys rendered
  12 pad slots, 13 keys

2Demo take0.6 s

Demo loads a built-in synthetic recording (knocks, thuds, plucked notes) so the app is playable without a microphone.

• ✓Demo take sliced into hits
  12 hits

3Record from the microphone3.1 s

Rec starts recording at once; the waveform scrolls in live. Rec again stops, analyses and saves the take. (The microphone here is a fake device playing the demo file.)

• ✓Recording sliced into hits
  5 hits in 0:02
• ✓Saved as a take with its own link
  http://localhost:8788/t/DKvu8vabmOOJ

4Import a file0.9 s

Import opens a file (here the walkthrough take: footsteps, knocks, a plucked A3, a quiet knock, a wind gust, glass, bird chirps, dropped keys). Analysis runs off the main thread and the take is saved.

• ✓Analysis under 1 s for 10 s of audio
  sliced in 53 ms
• ✓Every broadband hit found (±40 ms)
  11/11
• iBird chirp at 7.6 s (narrowband, a known weak spot)
  not sliced at the default sensitivity: candidate strength 0.14 vs threshold 0.25; raise sensitivity to get it
• ✓No false hit in the wind gust
  4.5–5.4 s clean

Ground truth: footstep 0.4s · footstep 1s · footstep 1.6s · knock 2.3s · knock 2.55s · pluck 3.2s · quiet knock 5.8s · glass 6.4s · bird chirp 7.6s · keys 8.3s · footstep 9.3s · bell 10.3s

5Keys arm the most tonal slice0.6 s

After analysis the keys arm the slice that makes the best instrument (pitch confidence × ring length), not slice 1. Its detected root labels the keys.

• ✓Plucked A3 is armed
  KEYS PLAY Slice 6/11 A3 +5¢
• ✓Root label within 10¢ of the true pitch
  label 220.64 Hz vs true 220.69 Hz (-0.4¢)
• ✓A clear pitch is not marked approximate (no ≈)
  KEYS PLAY Slice 6/11 A3 +5¢

6Pads play trimmed slices1.3 s

A pad plays its slice from just before the attack to where the sound dies into the background, not to the next hit. Faint regions on the waveform are what gets trimmed.

• ✓Plays the hit, then stops well before the next one
  played 0.34 s; next hit is 0.60 s after this one
• ✓No DC offset in playback (removed at import)
  mean 0.0004 (the file has +0.010 offset and 6 Hz rumble)
• iStart of playback
  peak in first ms 0.007: a 2 ms fade-in, no click

7Normalization3.2 s

With Norm on (default), every slice plays at the same peak level, so a distant knock is as playable as a close one. Norm off plays slices at their recorded level.

• ✓Norm on: both peak near -1 dBFS
  knock -1.0 dBFS, quiet knock -1.0 dBFS
• ✓Norm off: the quiet knock is ~10 dB softer
  knock -5.8 dBFS, quiet knock -13.8 dBFS (8.0 dB apart)

8Waveform: tap, double-tap, arrows3.9 s

Tapping a slice selects and auditions it (Delete acts on the selection). Double-tapping arms it on the keys. The ‹ › arrows step the armed slice. A glass and a bell have no clean harmonic series, so their roots are best guesses, marked ≈ with no cents: the glass by its lowest partial, the bell by its hum (the right note, an octave below the strike).

• ✓Tap auditions the slice
  peak -1.0 dBFS
• ✓Trash button appears under the selected marker
• ✓Double-tap arms the slice
  KEYS PLAY Slice 8/11 ≈ A5
• ✓Glass root: ≈ and its lowest partial (A5)
  KEYS PLAY Slice 8/11 ≈ A5
• ✓Bell root: ≈ and the prime's note name (A, any octave)
  KEYS PLAY Slice 11/11 ≈ A3 (a period detector alone finds 44 Hz, the common divisor)
• ✓‹ steps back to the pluck
  KEYS PLAY Slice 6/11 A3 +5¢

9Keys: pitch matches the label7.8 s

Each key plays the armed slice at that key's pitch, tuned against the detected root. Touching low on a key plays it dry (no smear). Measured: the pitch of what comes out of the speakers.

• ✓Root key sounds its label (±10¢)
  heard 220.00 Hz, key is 220.00 Hz (-0.0¢)
• ✓Lowest key sounds its label (±10¢)
  heard 130.82 Hz, key is 130.81 Hz (+0.1¢)
• ✓Highest key sounds its label (±10¢)
  heard 261.62 Hz, key is 261.63 Hz (-0.0¢)

10Keys: a held note sustains9.3 s

Held past the end of its slice, a pitched note plays its natural decay, then hovers where it has fallen 12 dB: each grain comes from a random in-tune spot there, so there is no fixed loop to hear repeating. Release fades it out.

• ✓Still sounding at 3–4 s (slice is ~2 s)
  level -10.0 dB below the peak
• ✓Sustain is steady (no re-strike or pulsing)
  level varies 0.1 dB over 3–3.9 s
• ✓No fixed loop (the held sound never replays itself)
  best 100–300 ms self-match stands 0.03 above the typical one (the old fixed loop scored 0.41)
• ✓Release fades out
  silent 0.26 s after release

11Smear7.1 s

Finger height on a key is the smear: low is dry, high freezes the sound into a grain cloud (live PaulStretch). Smeared notes release more slowly.

• ✓Smeared release is longer (≥ 0.4 s)
  sounds 1.06 s after release
• iCloud level variation 1–2.4 s
  15.9 dB

12Computer keyboard2.3 s

With a hardware keyboard: number row plays pads, A…K plays the keys, ← → step the armed slice, Z X shift octave.

• ✓1 plays pad 1
  peak -2.9 dBFS
• ✓→ arms the next slice
  KEYS PLAY Slice 6/11 A3 +5¢ → KEYS PLAY Slice 7/11 Unpitched → C3
• ✓X shifts the keys up an octave
  C3 → C4
• ✓A plays the lowest key

13MIDI7.9 s

MIDI channel 1 plays pads from C1 (note 36); channels 2–16 play slices 1–15 pitched; velocity sets level; mod wheel sets smear. (Driven through the hook a native iPad wrapper uses: window.fieldSamplerMidi.)

• ✓Velocity 64 is ~12 dB softer than 127 (level = velocity²)
  11.9 dB
• ✓Pitched channel plays A4 (±10¢)
  heard 440.03 Hz (+0.1¢)
• ✓Mod wheel smears (long release)
  sounds 0.95 s after note off

14Delete and undo4.1 s

Delete a transient with the trash button under its marker (or the Delete key). Its audio is dropped; Undo brings it back.

• ✓Trash removes the hit
  11 → 10
• ✓Delete key removes the selected hit
  10 → 9
• ✓Deletions saved to the take
  server has 2 deleted
• ✓Undo twice restores both
  11 hits

15Add a transient1.7 s

Long-press on the waveform adds a transient at the finger. It gets its own natural end like any other hit.

• ✓Long-press adds a hit
  11 → 12
• ✓Undo removes it

16Sensitivity1.0 s

The slider beside the waveform filters precomputed candidates: instant, no re-analysis. Short ticks along the bottom show what the next stretch of the slider would add.

• ✓More ≥ default ≥ fewer
  139 / 11 / 11
• ✓Back at the middle restores the count
  11 (was 11)

17Name, history and link2.5 s

Tap the name to rename. The ▾ menu lists this browser's takes and copies the take's link. Edits autosave.

• ✓Rename saved to the server
  server name: Walkthrough take
• ✓History lists all three takes
  Walkthrough take · take-1011-2029 · demo
• ✓Copy link copies the take URL
  http://localhost:8788/t/ypmEBEEmeaKi

18Shared link: view only, with a preview card0.8 s

Someone opening the link (another browser) gets the same take and can play it, but not change it. Messages and Slack show a preview card with the name and waveform.

• ✓Opens as view only
• ✓Same name
• ✓Link preview has title and image
  Walkthrough take · Field Sampler · 11 hits · 0:12. Open it to play on pads and keys.
• ✓Preview image served
  200 image/png

19Reopen a take from history1.1 s

Choosing a take in the menu opens it (its URL becomes the address), with its own slicing and edits.

• ✓Switched to the recorded take
  http://localhost:8788/t/DKvu8vabmOOJ

20Portrait2.2 s

Portrait works too (secondary): the same single screen, stacked.

• ✓Fits the screen: no scrolling, keys fully visible
  overflow 0 px wide, 0 px tall; keys end 14 px above the bottom

21Console0.0 s

Errors the page logged during the whole walkthrough.

• ✓No page errors
  none