machine: Fretwire pickups, wiring and bodies

CHANGELOG.md

@@ -19,6 +19,19 @@ GitHub are its section here (`tools/release.sh` copies them), so add to
   pitch when hit hard, cymbals bloom into a wash, and a closed hat chokes
   an open one. Five presets. See docs/41.
 
+- **Fretwire gets pickups, wiring and bodies.** The bass and guitar have
+  a second page. Choose the neck pickup, the bridge pickup, both, or both
+  out of phase. Pick single coil, P-90, humbucker or split coil, and set
+  how close the magnets sit. Real tone and volume pots roll the tone into
+  the mids and clean up an amp's drive. The strings now share a body,
+  SOLID, SEMI, HOLLOW or ACOUSTIC, that colors their decay and can be
+  miked (AIR). There is also an under-saddle piezo, and open strings that
+  ring in sympathy. New presets include twin-humbucker, p90-crunch,
+  semi-hollow, out-of-phase and acoustic guitars, and jazz-both, p-bass,
+  hollow and acoustic basses. Saved bass and guitar parts now sound
+  slightly different on the default solid body's dead spots; set COUPLE
+  to 0 for the old sound. See docs/41.
+
 - **Separate STOP and PLAY.** Pressing STOP again while stopped returns
   to the loop's start, or to the song's start with the loop off.
 

bench/golden/bass.txt

@@ -1,6 +1,6 @@
 # bench goldens for bass: case sha256(f32 L ++ f32 R) [nonharm_db thd_db]
-notes 6937fb38af3c6ab2b3f575df95592cb75bfaa4e2ade23b32783fe0673f6625ec
-velocity 8f5a032f4c439643181d79611e3c5100dc02797ac9f5d7031fa1a55fd966949d
-held a4caf9e0aeeda62291a25bb51a33fef6a531452d7d77156581ca48d9b97aa09c -72.0 -1.0
-high 84f46ca1cfca042bd39e28fcba891fa91d158445cb51123e6585f0aaba350f8e -72.8 -29.3
-chord 4296a539b9dec08c355bfd665e1ec945bf353d3bdeff374fc2024f2f654fe8a4 2.5 6.5
+notes 26c8fbcd88dbabbc9293e7517398a1f47c0541fcf173d9577be80527060133bc
+velocity e60975486103d37400cd3dbccc162edc2d735a715ee420e854138f9311b9aff8
+held 8125b1ff57d4f10926925f91d130a37e639735d320634c49e9465917fc07247e -72.2 -4.9
+high 4b58d8ef0d9247e475265d5bd28b4d393fee6135ab007aab86bb60a33c0a7205 -73.0 -30.3
+chord f0e284d9782fc34fdeaad0e3fecc6f463ca87c55a344069b7a6ed4d56fb5db52 2.8 5.4

bench/golden/guitar.txt

@@ -1,6 +1,6 @@
 # bench goldens for guitar: case sha256(f32 L ++ f32 R) [nonharm_db thd_db]
-notes f27519fbf925fbf57bf4fd274367307371289a1fdf90937b267b14889ebcf57d
-velocity 089cd20ccd61b8cddcbb6afefe6152e92a7a17da4f780ce44941e5443067fa0c
-held aaac8b719a9606f6517274cd64d52951f0b01b0f3be3fda4a29eaec92efcf8eb -73.6 -3.3
-high 8cadbe64df4d354ea25f585a7be87a4014bfc5e93a637802ac220d588d9ebe04 -73.0 -14.6
-chord 8a259ffabb8aff4de7e3ee795a06933fd11fc4b31f8c588182e32ad9ba398807 2.2 0.8
+notes 1e054305a36bbbda110a7127422c00e903ad5dfb591ddc043808769719bb3979
+velocity 6180d5c8e7ed78bfb59c802bb6e54d58257caa61d8d6d36ee4d9dbb2666cce49
+held 1a969eb89554e1597baf03dec5bfd3aa46b7da92fa843037a8840aae3d40f8aa -73.7 -3.8
+high 281079ab8def8d9e675ae3021844ed1b4d4390f41aec4a11c2baedc35e78b80e -73.1 -14.9
+chord 968bddfb42b804497d8ac22a62bed88de9514a0d2a842b82de239d0ec510d208 1.9 0.4

docs/20-machine-reference.md

@@ -60,10 +60,22 @@ project or preset stores (docs/19): real units for knobs, the option
 | `bs-soft` | PLUCK | SOFT | 0.05 … 6 | 2 | exp |
 | `bs-shape` | PLUCK | SHAPE | 0 … 1 | 0 | linear |
 | `bs-noise` | PLUCK | NOISE | 0 … 1 | 0.15 | pow |
-| `bs-pickup` | PICKUP | POS | 0.04 … 0.5 | 0.2 | linear |
-| `bs-hand` | PICKUP | HAND | 0 … 12 | 5 | linear |
-| `bs-tone` | PICKUP | TONE | 300 … 12000 | 3200 | exp |
-| `bs-res` | PICKUP | RES | 0 … 1 | 0.3 | linear |
+| `bs-hand` | PLUCK | HAND | 0 … 12 | 5 | linear |
+| `bs-pickup` | PICKUPS | NECK | 0.04 … 0.5 | 0.2 | linear |
+| `bs-pickup-b` | PICKUPS | BRIDGE | 0.04 … 0.5 | 0.1 | linear |
+| `bs-sel` | PICKUPS | SELECT | 0 NECK / 1 BOTH / 2 BRIDGE / 3 OUT | 0 | switch |
+| `bs-type-n` | PICKUPS | N TYPE | 0 SINGLE / 1 SPLIT / 2 HUMBUCK | 0 | switch |
+| `bs-type-b` | PICKUPS | B TYPE | 0 SINGLE / 1 SPLIT / 2 HUMBUCK | 0 | switch |
+| `bs-height` | PICKUPS | HEIGHT | 0 … 1 | 0 | linear |
+| `bs-tone` | WIRING | RESO | 300 … 12000 | 3200 | exp |
+| `bs-res` | WIRING | PEAK | 0 … 1 | 0.3 | linear |
+| `bs-tpot` | WIRING | TONE | 0 … 1 | 1 | linear |
+| `bs-vol` | WIRING | VOL | 0 … 1 | 1 | linear |
+| `bs-body` | BODY | BODY | 0 SOLID / 1 HOLLOW / 2 ACOUSTIC | 0 | switch |
+| `bs-couple` | BODY | COUPLE | 0 … 2 | 1 | linear |
+| `bs-air` | BODY | AIR | 0 … 1 | 0 | pow |
+| `bs-piezo` | BODY | PIEZO | 0 … 1 | 0 | pow |
+| `bs-symp` | BODY | SYMP | 0 … 1 | 0 | linear |
 | `bs-thump` | FEEL | THUMP | 0 … 1 | 0.5 | linear |
 | `bs-buzz` | FEEL | BUZZ | 0 … 1 | 0 | linear |
 | `bs-motion` | FEEL | MOTION | 0 AUTO / 1 BEND / 2 SLIDE | 0 | switch |
@@ -74,13 +86,17 @@ project or preset stores (docs/19): real units for knobs, the option
 
 Presets:
 
+- `acoustic` — An acoustic bass guitar, miked, with some piezo and the open strings in sympathy
 - `default` — Fingers on the neck pickup: roundwounds, direct
 - `fingers-bridge` — Fingers over the bridge pickup: nasal, growly, more mids
 - `flatwound` — Old flatwounds, tone rolled off: short, thumpy, dub and Motown
+- `hollow` — A hollow violin bass on flatwounds: short, woody, a little air
+- `jazz-both` — Both single coils of a Jazz-type bass, fingers: fitted to Karoryfer's Growlybass
+- `p-bass` — A split-coil P-type pickup, roundwounds, tone a little back: the punchy middle of a mix
 - `palm-mute` — Muted with the palm: a short pick thud
 - `pick` — Played with a pick near the bridge: bright attack, click, rounder sustain
-- `pop` — Popped string: pulled and snapped, hard push, buzz
-- `slap` — Thumb slap over the end of the neck: narrow strike, fret rattle, bright
+- `pop` — Popped string over a bridge humbucker: pulled and snapped, hard push, buzz
+- `slap` — Thumb slap over the end of the neck, a bridge humbucker: narrow strike, fret rattle, bright
 
 ## concoction
 
@@ -671,10 +687,22 @@ Presets:
 | `gt-soft` | PLUCK | SOFT | 0.05 … 6 | 1 | exp |
 | `gt-shape` | PLUCK | SHAPE | 0 … 1 | 0.4 | linear |
 | `gt-noise` | PLUCK | NOISE | 0 … 1 | 0.15 | pow |
-| `gt-pickup` | PICKUP | POS | 0.04 … 0.5 | 0.24 | linear |
-| `gt-hand` | PICKUP | HAND | 0 … 12 | 0 | linear |
-| `gt-tone` | PICKUP | TONE | 300 … 12000 | 4500 | exp |
-| `gt-res` | PICKUP | RES | 0 … 1 | 0.4 | linear |
+| `gt-hand` | PLUCK | HAND | 0 … 12 | 0 | linear |
+| `gt-pickup` | PICKUPS | NECK | 0.04 … 0.5 | 0.24 | linear |
+| `gt-pickup-b` | PICKUPS | BRIDGE | 0.04 … 0.5 | 0.07 | linear |
+| `gt-sel` | PICKUPS | SELECT | 0 NECK / 1 BOTH / 2 BRIDGE / 3 OUT | 0 | switch |
+| `gt-type-n` | PICKUPS | N TYPE | 0 SINGLE / 1 P-90 / 2 HUMBUCK | 0 | switch |
+| `gt-type-b` | PICKUPS | B TYPE | 0 SINGLE / 1 P-90 / 2 HUMBUCK | 0 | switch |
+| `gt-height` | PICKUPS | HEIGHT | 0 … 1 | 0 | linear |
+| `gt-tone` | WIRING | RESO | 300 … 12000 | 4500 | exp |
+| `gt-res` | WIRING | PEAK | 0 … 1 | 0.4 | linear |
+| `gt-tpot` | WIRING | TONE | 0 … 1 | 1 | linear |
+| `gt-vol` | WIRING | VOL | 0 … 1 | 1 | linear |
+| `gt-body` | BODY | BODY | 0 SOLID / 1 SEMI / 2 HOLLOW / 3 ACOUSTIC | 0 | switch |
+| `gt-couple` | BODY | COUPLE | 0 … 2 | 1 | linear |
+| `gt-air` | BODY | AIR | 0 … 1 | 0 | pow |
+| `gt-piezo` | BODY | PIEZO | 0 … 1 | 0 | pow |
+| `gt-symp` | BODY | SYMP | 0 … 1 | 0 | linear |
 | `gt-thump` | FEEL | THUMP | 0 … 1 | 0.3 | linear |
 | `gt-buzz` | FEEL | BUZZ | 0 … 1 | 0 | linear |
 | `gt-motion` | FEEL | MOTION | 0 AUTO / 1 BEND / 2 SLIDE | 0 | switch |
@@ -685,13 +713,18 @@ Presets:
 
 Presets:
 
+- `acoustic` — A flat-top acoustic, miked, with a little under-saddle piezo and the open strings ringing along
 - `bridge` — Picked on the bridge pickup: thin, bright, cutting; for crunch and leads into an amp
 - `default` — Picked, neck pickup, open position: the clean electric
 - `fingers` — Fingerstyle, thumb and fingers over the neck: round and soft
-- `funk` — Bright, tight, short: bridge-and-middle funk chops
-- `jazz` — Archtop jazz: neck pickup, tone rolled off, flatwound thump
-- `palm-mute` — Palm-muted picking: a short chug, give it a high-gain amp
+- `funk` — Middle and bridge single coils together: the bright, quacky funk chop
+- `jazz` — Archtop jazz: a hollow body, the neck humbucker, tone rolled back, a little air
+- `out-of-phase` — Neck and middle out of phase: the thin, hollow, nasal tone
+- `p90-crunch` — A bridge P-90 set close to the strings: fat, raw mids that break up early in an amp
+- `palm-mute` — Palm-muted picking on a bridge humbucker: a short, tight chug for a high-gain amp
+- `semi-hollow` — A semi-hollow with two humbuckers: warm, woody, a touch of sympathetic ring
 - `slide` — Bottleneck slide: long sustain, pitch curves glide fret by fret with the rasp
+- `twin-humbucker` — Two humbuckers together, picked near the bridge, direct: fitted to Karoryfer's Emily
 
 ## jp8
 

docs/21-production-guide.md

@@ -404,6 +404,13 @@ Leave pads alone; they're already even.
   or `bass-grind`. Guitars: `guitar-clean`, `guitar-crunch`,
   `guitar-lead`, `guitar-heavy`. Leave CAB on unless another cabinet
   follows, and use BLEND, not a parallel track, to keep the DI's low end.
+- **Pick the instrument before the amp.** Fretwire's GUITAR or BASS page
+  is the instrument: pickups (SELECT, TYPE, HEIGHT), wiring (TONE and VOL
+  pots) and BODY (docs/41). Start from a preset: `twin-humbucker` or
+  `p90-crunch` for a driven amp, `funk` for chops, `jazz` or
+  `semi-hollow` for warm clean parts; on bass, `jazz-both`, `p-bass` or
+  `hollow`. Roll VOL back to clean up an amp's drive. The `acoustic`
+  presets are miked bodies with a little piezo: skip Ampstack for them.
 - `chorus2`: `juno-i` / `juno-ii` for pads and keys. Never on bass or
   kick; it smears the low end out of mono.
 - **Share spaces with sends.** Put a fully wet reverb on a bus and send

docs/41-physical-models.md

@@ -1,4 +1,4 @@
-# 41 — Physical models: Hammerwork Grand and Skinwork Kit
+# 41 — Physical models: Hammerwork Grand, Skinwork Kit, Fretwire bodies
 
 Two machines synthesize their sound by simulating the instrument's
 mechanics, sample by sample:
@@ -8,6 +8,10 @@ mechanics, sample by sample:
 - `kit` (**Skinwork Kit**) is a drum kit: sticks and beaters strike
   membranes and cymbals.
 
+Fretwire's bass and guitar (`bass`, `guitar`) build the instrument around
+their waveguide strings the same way: pickups, wiring and a body every
+string shares (§Fretwire: pickups, wiring and bodies).
+
 They share a small layer of physical-modeling kernels,
 `kernels/10-physical/`. **Status:** built 2026-10-16 on branch
 `claude/physical-piano-drums`.
@@ -25,6 +29,9 @@ Code:
   modes, generated by `tools/fit/bessel.py`.
 - `kernels/06-voices/piano.fy` and `machines/grand/`: the piano.
 - `kernels/06-voices/kit.fy` and `machines/kit/`: the kit.
+- `kernels/06-voices/string.fy` (the strings and pickups),
+  `kernels/06-voices/string_body.fy` (bridge, body, wiring, open strings)
+  and `machines/bass/`, `machines/guitar/`: Fretwire.
 
 ## The building blocks (`kernels/10-physical`)
 
@@ -151,19 +158,137 @@ The lower note of each tom pair, and the second kick, sit a little lower
 **Cost:** about 530 ns per sample in Debug for the bench hit sequence.
 The render word, like the piano's, renders without NEON lanes.
 
+## Fretwire: pickups, wiring and bodies
+
+**Status:** built 2026-10-16 on branch `claude/fretwire-bodies`, stacked
+on `claude/physical-piano-drums` (it needs shared state, docs/04).
+
+Fretwire's strings were already waveguides fitted to recordings. What
+they lacked was the instrument: one pickup point and a resonant lowpass
+stood for every electric, and nothing joined the strings. Each machine
+now has a second page (GUITAR or BASS) with three sections, and every
+string drives one shared body through the bridge. The shared word
+(`fw-body-render`, period 1) runs after the strings each sample.
+
+### Pickups
+
+Two pickups, NECK and BRIDGE, each at its own point along the string
+(a fraction of the open string, from the bridge). A coil hears the string
+where it sits, so its comb notches move string to string and up the neck,
+as on the instrument. SELECT picks NECK, BOTH, BRIDGE, or OUT (both, the
+bridge coil reversed). Two coils in parallel share the output by
+inductance, each heard in the proportion of the other's.
+
+| TYPE | Taps | Inductance | Sounds |
+|---|---|---|---|
+| SINGLE | one point | 1x | the bright, glassy single coil |
+| P-90 (guitar) | a wide bobbin's edges, 0.036 of the string apart | 1.8x | fatter, rawer mids |
+| HUMBUCK | two coils 18 mm apart | 1.8x | warmer: the two coils' views cancel near an open string's 36th harmonic (3 dB down at the 18th), and the resonance drops to 0.75x |
+| SPLIT (bass) | one point, the low strings' half 1.2% further toward the neck | 1.4x | a P-type bass |
+
+HEIGHT moves the magnets toward the strings. The coil's output is the
+string's velocity times 1 / [1 - k x]^2, x the string's displacement over
+it [Horton and Moore 2009]. A string swinging toward the magnet sees more
+flux than swinging away, so loud notes gain even harmonics and some
+level.
+
+### Wiring
+
+The coils drive the cable's capacitance, the pots and the amp's input:
+
+    H(s) = 1 / (1 + (R + sL) (sC + G + sCt / (1 + s Rt Ct)))
+
+- **RESO** and **PEAK** (the old TONE and RES, same ids) are a single
+  coil's loaded resonance with the tone pot open. C and G are solved from
+  them for the selected coils' L and R, so a humbucker or two coils in
+  parallel move the resonance by the square root of their inductance.
+- **TONE** is the tone pot: down from 1 its resistance (250 k, audio
+  taper) brings in the tone capacitor (22 nF guitar, 47 nF bass). At 0
+  the resonance drops to around 700 Hz: the "woman tone". At 1 the
+  branch is open, the filter is the old 2-pole one, and the output nulls
+  against the old Fretwire's at the 24-bit floor (COUPLE 0).
+- **VOL** is the volume pot: an audio taper, plus the treble its wiper
+  resistance loses into the cable. Turning it down cleans up Ampstack's
+  drive the way a guitarist does.
+
+The 3rd-order H goes to z by the bilinear transform, prewarped at the
+resonance, once a block.
+
+### Body
+
+Every string pushes on the bridge with the wave arriving there and moves
+with the bridge's velocity [Gough 1981; Woodhouse 2004]. The bridge is
+the body's modes: 8 low modes per body (the air cavity, the first top and
+back modes), then 40 dense modes spread evenly to a few kHz with
+overlapping bandwidths. A mode takes energy from string partials near it,
+so notes there decay faster and swell into the body: dead spots on a
+solid body, the wood of a hollow one. The 12-mode board taught us the
+dense part matters: a dozen peaks alone sound boxy and honky.
+
+| BODY | Coupling | Character |
+|---|---|---|
+| SOLID | weak, high Q | neck and body dead spots; almost no air |
+| SEMI (guitar) | a centre block | some wood, sustain kept |
+| HOLLOW | an archtop, or a violin bass | woody, shorter, an air resonance near 110 Hz (bass 88) |
+| ACOUSTIC | a flat-top, or an acoustic bass guitar | strong: 98 Hz air, 196 Hz top (bass 72 / 128) |
+
+The low modes follow published guitar mobility and radiation
+measurements in shape, not any one instrument (our own estimates).
+
+- **COUPLE** scales the bridge coupling. 0 is a rigid bridge, the old
+  Fretwire.
+- **AIR** mixes in the body's radiated sound: its modes' acceleration
+  and, above them, the bridge force as a resistance. At 1 on an acoustic
+  body it sits at the pickups' level. A solid body radiates about 40 dB
+  less, as an unplugged electric does.
+- **PIEZO** mixes an under-saddle piezo: the bridge force itself, bright
+  and direct.
+- **SYMP** rings the open strings in sympathy. Each open string is a
+  delay loop in the shared region, driven by the bridge and pushing back
+  on it. A string a note is played on is muted. The strings are heard
+  through the pickups and the body.
+
+### Fitted against recordings
+
+`tools/fit/string_fit.py` measures the attack spectrum (harmonics 1-16,
+20-80 ms) and each harmonic's T60. A coordinate-descent fit over the
+pickup, pluck, wiring and decay knobs, scored on both, set two presets:
+
+| Preset | Reference | Error per harmonic, start → fit |
+|---|---|---|
+| `guitar` twin-humbucker | Karoryfer Emily, C3, both humbuckers, direct | 11.0 → 7.5 dB |
+| `bass` jazz-both | Karoryfer Growlybass, C2 (their c3), both pickups, direct | 12.8 → 7.8 dB |
+
+What still differs: the guitar reference's spectrum falls smoothly where
+ours keeps the pluck's and pickups' comb notches. The bass reference
+shows them (its 5th harmonic is 30 dB down), so they are real. But a pick
+and two pickups fill them in more than the model does.
+
+### Cost
+
+The shared body makes the strings render in lockstep, one voice at a
+time. In ReleaseFast the guitar's chord case went from 176 to 480 ns per
+sample (2.3% of a core). SYMP adds about 100 ns while it is up.
+
 ## Presets
 
 - `grand`: default, bright-pop, felt-ballad, honky-tonk, sustain-wash,
   dry-studio.
 - `kit`: default, jazz, rock, funk-dry, gong-wash.
+- `guitar` (new or reworked here): twin-humbucker, p90-crunch,
+  semi-hollow, out-of-phase, acoustic; jazz is now a hollow archtop on
+  the neck humbucker, funk the middle and bridge single coils together.
+- `bass`: jazz-both, p-bass, hollow, acoustic; pop and slap are on a
+  bridge humbucker.
 
 ## Next
 
 - **Fretwire and Rhodes.** Fretwire could take `contact-solve` for the
-  pluck and fret buzz, and moving-bridge coupling for its two-stage decay.
-  Rhodes could become a struck tine-and-tonebar mode pair with an
-  implicit hammer.
+  pluck and fret buzz. Its moving bridge and sympathetic strings are
+  built (§Fretwire). Rhodes could become a struck tine-and-tonebar mode
+  pair with an implicit hammer.
 - **Lane mode.** Splitting the render into a lane-eligible word, or
   raising the stash limit, would roughly halve the cost.
-- **Sympathetic strings.** These need a shared board across voices: a
-  host-side bus or a single-voice piano.
+- **Sympathetic strings in the Grand.** Fretwire's open strings show the
+  way: a shared region holding the undamped strings, driven by the
+  bridge.