Feature/audio quality improvements

CLAUDE.md

@@ -7,7 +7,7 @@ TUI step sequencer / drum machine / synth in Rust. All DSP from scratch.
 ```bash
 cargo build          # dev build
 cargo build --release
-cargo test           # 23 tests, runs in <1s
+cargo test           # 55 tests, runs in <1s
 cargo run            # launch TUI
 ```
 
@@ -46,7 +46,7 @@ Two-thread model: UI thread (ratatui + crossterm) and audio thread (cpal/CoreAud
 - `drum_voice.rs` — per-track DSP (kick, snare, hats, etc.), params: tune/sweep/color/snap/filter/drive/decay/volume
 - `synth_voice.rs` — polyphonic synth DSP, 2 oscillators, 2 envelopes, filter with own ADSR
 - `mixer.rs` — channel mixing, send effects
-- `effects.rs` — reverb, delay, compressor, saturator
+- `effects.rs` — FDN reverb, delay, compressor, saturator, lookahead limiter, sidechain envelope, oversampler
 - `display_buffer.rs` — lock-free audio→UI buffer for waveform display
 - `fft.rs` — FFT for spectrum analyzer
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "textstep"
-version = "1.3.0"
+version = "1.4.0"
 edition = "2024"
 
 [dependencies]

README.md

@@ -1,42 +1,42 @@
 <div align="center">
 
-# T E X T S T E P
+# 🎛️ T E X T S T E P 🎹
 
 **A terminal-based step sequencer, drum machine, and synthesizer built entirely in Rust.**
 
-All DSP from scratch — no samples, no external audio libraries. Just your terminal and your speakers.
+♪ All DSP from scratch — no samples, no external audio libraries. Just your terminal and your speakers. ♫
 
 [![Rust](https://img.shields.io/badge/Rust-1.70%2B-orange?logo=rust&logoColor=white)](https://www.rust-lang.org/)
 [![License: GPL v2](https://img.shields.io/badge/License-GPL_v2-blue.svg)](https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html)
 [![Platform: macOS](https://img.shields.io/badge/Platform-macOS-lightgrey?logo=apple&logoColor=white)](https://www.apple.com/macos/)
 [![Platform: Linux](https://img.shields.io/badge/Platform-Linux-lightgrey?logo=linux&logoColor=white)](https://www.kernel.org/)
 [![Audio: CoreAudio / ALSA](https://img.shields.io/badge/Audio-CoreAudio_|_ALSA-green)](https://developer.apple.com/documentation/coreaudio)
 [![TUI: ratatui](https://img.shields.io/badge/TUI-ratatui-purple)](https://ratatui.rs/)
-[![Lines of Code](https://img.shields.io/badge/Lines_of_Code-20k-informational)]()
-[![Tests](https://img.shields.io/badge/Tests-48_passing-brightgreen)]()
+[![Lines of Code](https://img.shields.io/badge/Lines_of_Code-17k-informational)]()
+[![Tests](https://img.shields.io/badge/Tests-55_passing-brightgreen)]()
 
 ![TextStep Demo](assets/demo.gif)
 
 </div>
 
 ---
 
-## Features
+## ✨ Features
 
-- **8 Drum Tracks** — Kick, Snare, Closed HiHat, Open HiHat, Ride, Clap, Cowbell, Tom — each fully synthesized with 8 tweakable sound parameters
-- **Dual Polyphonic Synths** — Synth A + Synth B with DJ-style crossfader, each with 2 oscillators + sub, 2 ADSR envelopes, resonant filter, dual LFOs with 6 waveforms, independent patterns and kits
-- **32-Step Sequencer** — 10 patterns and 8 kit slots with per-pattern BPM and swing
-- **16 Scene Slots** — snapshot and recall full instrument states (all patterns, kits, BPM, swing) with queued or immediate switching
-- **Send Effects Chain** — Schroeder reverb, tempo-synced filtered delay, tube saturator, SSL-style glue compressor
-- **Live Performance** — drum pads, real-time recording, pattern queuing, scene-based arrangement
-- **Mouse Support** — click the grid, drag parameters Ableton-style, audition sounds from the activity bar
-- **Project System** — save/load `.tsp` files, standalone kit export, preset browser
-- **Collapsible Panels** — minimize/expand synth, drum knobs, and waveform sections; auto-adapts to small terminals
-- **Spectrum Analyzer** — real-time FFT spectrum display and VU meter with 90s Hi-Fi LED aesthetic
+- 🥁 **8 Drum Tracks** — Kick, Snare, Closed HiHat, Open HiHat, Ride, Clap, Cowbell, Tom — each fully synthesized with 8 tweakable sound parameters
+- 🎹 **Dual Polyphonic Synths** — Synth A + Synth B with DJ-style crossfader, each with 2 oscillators + sub, 2 ADSR envelopes, resonant filter, dual LFOs with 6 waveforms, independent patterns and kits
+- 🔲 **32-Step Sequencer** — 10 patterns and 8 kit slots with per-pattern BPM and swing
+- 🎬 **16 Scene Slots** — snapshot and recall full instrument states (all patterns, kits, BPM, swing) with queued or immediate switching
+- 🔊 **Pro Audio Engine** — FDN reverb (8-line stereo), tempo-synced delay, 2×-oversampled tube saturator, SSL-style glue compressor, lookahead limiter, sidechain compression (kick ducks synths)
+- 🎤 **Live Performance** — drum pads, real-time recording, pattern queuing, scene-based arrangement
+- 🖱️ **Mouse Support** — click the grid, drag parameters Ableton-style, audition sounds from the activity bar
+- 💾 **Project System** — save/load `.tsp` files, standalone kit export, preset browser
+- 📐 **Collapsible Panels** — minimize/expand synth, drum knobs, and waveform sections; auto-adapts to small terminals
+- 📊 **Spectrum Analyzer** — real-time FFT spectrum display and VU meter with 90s Hi-Fi LED aesthetic
 
-Ships with **10 demo scenes** ready to play: Acid Techno, Classic House, Deep House, Driving Techno, Lo-Fi Hip Hop, Trance, Drum & Bass, Electro Funk, Dub Techno, and Ambient — each with matched drum patterns, synth patterns, and kits.
+Ships with **10 demo scenes** ready to play: 🎵 Acid Techno, Classic House, Deep House, Driving Techno, Lo-Fi Hip Hop, Trance, Drum & Bass, Electro Funk, Dub Techno, and Ambient — each with matched drum patterns, synth patterns, and kits.
 
-## Getting Started
+## 🚀 Getting Started
 
 ### Prerequisites
 
@@ -66,7 +66,7 @@ sudo apt-get install libasound2-dev   # Debian/Ubuntu
 Run the tests:
 
 ```bash
-cargo test    # 48 tests, runs in <1s
+cargo test    # 55 tests, runs in <1s
 ```
 
 ### Pre-built Binaries
@@ -79,9 +79,9 @@ Pre-built binaries for macOS (ARM, x86_64, universal) and Linux (x86_64) are ava
 xattr -d com.apple.quarantine ./textstep
 ```
 
-## Quick Manual
+## 🎚️ Quick Manual
 
-### Transport
+### ▶️ Transport
 
 | Key | Action |
 |-----|--------|
@@ -94,13 +94,14 @@ xattr -d com.apple.quarantine ./textstep
 | `L` | Cycle loop length: 8 / 16 / 24 / 32 |
 | `Shift+C` | Cycle compressor: Off / Light / Medium / Heavy / Max |
 | `Shift+T` | Cycle tube saturator: Off / Light / Medium / Heavy / Max |
+| `Shift+D` | Cycle sidechain duck: Off / Light / Medium / Heavy / Max |
 | `Shift+V` | Adjust master volume |
 | `<` / `>` | Swing ±5% |
 | `(` / `)` | Crossfader toward A / B |
 | Click `A` / `B` | Mute/unmute Synth A / B |
 | Click `C` | Reset crossfader to center |
 
-### Navigation
+### 🧭 Navigation
 
 | Key | Action |
 |-----|--------|
@@ -112,7 +113,7 @@ xattr -d com.apple.quarantine ./textstep
 | `~` | Toggle spectrum analyzer / VU meter |
 | `?` | Help overlay |
 
-### Sound Design
+### 🎛️ Sound Design
 
 Each drum track has 8 parameters across three pages:
 
@@ -126,7 +127,7 @@ Tweak with `Shift+Up/Down` (adjust value) or `Alt+Up/Down` (adjust and audition
 
 Mute (`Shift+M`) and Solo (`Shift+S`) are always accessible on any page.
 
-### Drum Pads
+### 🥁 Drum Pads
 
 The bottom keyboard row triggers sounds live:
 
@@ -136,7 +137,7 @@ The bottom keyboard row triggers sounds live:
 
 With record enabled and playback running, pad hits write steps at the playhead.
 
-### Patterns & Kits
+### 🔀 Patterns & Kits
 
 **Patterns** — 10 slots per section (Synth A, Synth B, Drums), each with its own step data:
 
@@ -153,13 +154,13 @@ With record enabled and playback running, pad hits write steps at the playhead.
 |-----|--------|
 | `1` through `8` | Switch to kit slot |
 
-### Dual Synths
+### 🎹 Dual Synths
 
 TextStep features two independent polyphonic synthesizers (**Synth A** and **Synth B**), each with its own patterns, kits, 2 oscillators + sub, noise, 2 ADSR envelopes, 24dB resonant filter, and LFO with 6 waveforms. Toggle all synth panels with `F2`. Each synth has its own pattern/kit selectors shown in the transport bar.
 
 Synth notes are triggered with `z` `x` `c` `v` when a synth grid is focused, with `Up/Down` for pitch and `(` `)` for octave shifts.
 
-### Scenes
+### 🎬 Scenes
 
 Scenes are snapshots of the full instrument state: which pattern and kit is selected for drums, Synth A, and Synth B, plus BPM and swing. Use them to arrange your track.
 
@@ -173,7 +174,7 @@ Scenes are snapshots of the full instrument state: which pattern and kit is sele
 | `D` | Delete scene |
 | `Esc` | Close browser |
 
-### File Operations
+### 💾 File Operations
 
 | Key | Action |
 |-----|--------|
@@ -189,7 +190,7 @@ Scenes are snapshots of the full instrument state: which pattern and kit is sele
 
 Projects are stored as JSON in `~/Library/Application Support/textstep/projects/`.
 
-## Architecture
+## 🏗️ Architecture
 
 ```
 ┌──────────────────────────────────────────────────┐
@@ -219,14 +220,14 @@ Projects are stored as JSON in `~/Library/Application Support/textstep/projects/
 
 Communication is lock-free via bounded crossbeam channels. The audio thread never blocks.
 
-### DSP — All From Scratch
+### 🔧 DSP — All From Scratch
 
 Every sound is synthesized in real-time with no external DSP dependencies:
 
 - **Drum voices** — TR-808/909-inspired kicks (sine + pitch envelope + resonant impulse), noise-blended snares, 6-oscillator metallic banks for hats and rides (Mutable Instruments Plaits-style inharmonic ratios), ring-modulated open hats, bandpass claps, detuned pulse cowbells, FM toms
-- **Synth voice** — dual oscillators, sub, noise, two ADSR envelopes, resonant SVF filter, 6-waveform LFO
-- **Effects** — Schroeder/Freeverb reverb (4 comb + 2 allpass), tempo-synced filtered delay, asymmetric tube saturator, feedforward RMS glue compressor with soft knee
-- **Primitives** — 1-pole HP/LP filters, state-variable filter, xorshift32 noise, tanh waveshaping
+- **Synth voice** — dual PolyBLEP anti-aliased oscillators, sub, noise, two ADSR envelopes, resonant SVF filter, 6-waveform LFO
+- **Effects** — 8-line FDN reverb with Householder feedback matrix (native stereo), tempo-synced filtered delay, 2×-oversampled asymmetric tube saturator, feedforward RMS glue compressor with soft knee, true-peak lookahead limiter, sidechain envelope follower
+- **Primitives** — 1-pole HP/LP filters, state-variable filter, xorshift32 noise, stereo decorrelation
 
 ### Source Map
 
@@ -238,7 +239,7 @@ Every sound is synthesized in real-time with no external DSP dependencies:
 | `src/sequencer/` | Data: patterns, transport, project serialization |
 | `src/presets/` | Preset browser: drum/synth sounds and patterns by genre |
 
-### Color Palette
+### 🎨 Color Palette
 
 Hardware/synthwave aesthetic — all rendered with UTF-8 block characters on a dark background.
 
@@ -311,7 +312,7 @@ textStep/
 └── LICENSE                  # GPL v2
 ```
 
-## Contributing
+## 🤝 Contributing
 
 Contributions are welcome! Please ensure:
 
@@ -329,6 +330,8 @@ This project is licensed under the [GNU General Public License v2.0](LICENSE).
 
 <div align="center">
 
-**Built with Rust** · **All DSP from scratch** · **Zero audio dependencies**
+🦀 **Built with Rust** · 🔊 **All DSP from scratch** · 🎵 **Zero audio dependencies**
+
+*"Any sufficiently advanced terminal is indistinguishable from a drum machine."*
 
 </div>