bass-foundry/docs/pitch.md

# Pitch source in the tracked plugins

Anvil, Lathe, Temper, Knurl, Planish, Braze and Forge follow the note the bass
plays. **Pitch from** in each header says where that note comes from.

- **AUDIO** detects the note from the audio. This is the default.
- **MIDI** takes the notes from MIDI input. In FL Studio, set the bass channel's
  MIDI output port and the effect's input port to the same number.
- **NOTE** uses a note you set, for example F1. The audio only starts and stops
  notes; nothing is detected. Most riddim drops sit on one or two roots, so this
  is the safest choice for growls, FM basses and anything detection struggles
  with. Click the note button next to NOTE to pick the note and its octave.

## When detection is unsure

Real basses are often not one clear note: FM growls, formant sweeps, detuned
reeses, layers and noise. Detection therefore stays put:

- A new note needs a steady pitch for 40 ms. A jump down an octave needs 80 ms
  and a jump up an octave 200 ms, because a misread octave is the commonest
  error.
- Inside a note, the tuning only moves when the pitch drifts more than a quarter
  of a semitone for good.
- When the pitch keeps reading differently from the note (about 40 ms of
  disagreeing reads, or 400 ms without any clear read), the note turns
  **unsure**. The NOTE readout then shows **?**.

While the note is unsure, a plugin never acts on a guess:

| Plugin | While unsure |
| --- | --- |
| Anvil | Plays your original sub instead of the sine (Enhance: adds nothing) |
| Lathe | Passes the audio unchanged |
| Knurl | Fades its texture out |
| Temper, Planish, Braze | Keep the tuning of the last sure note |
| Forge | Each module as above |

## Key lock and Follow bends

With AUDIO selected, the button next to the switch opens two options:

- **Key lock** lets detection pick only notes of a key: **Minor**, **Major**,
  or **Root only** (any octave of the root, so detection only picks the
  octave). Pick the root below. A drop in F minor with Key lock on F minor can
  no longer read an F♯.
- **Follow bends** retunes on every bend and vibrato and switches notes after
  10 ms, as the plugins did before. It follows slides and 808 glides closely,
  but it flickers on growls. Leave it off unless the bass is clean and bends a
  lot.

## Measuring detection on your own stems

`cargo run -p common-dsp --release --example tracker_report` scores the
detection on a set of synthetic stems (growls, wobble, reese, formant bass, 808
slide, layered drop, noise riser). Pass WAV files to score real stems:

```text
cargo run -p common-dsp --release --example tracker_report -- --note F1 drop.wav
```

It prints note starts per second, the share of time with a wrong sure note, and
the share of time detection was unsure.