Backing Tracks - v0.7

A terminal-based backing track player that uses the BTML (Backing Track Markup Language) DSL. Generate complete backing tracks with chords, bass, drums, and auto-generated melodies with real-time scale visualization!

What Works

✅ Parse YAML-based BTML files
✅ Display track info and chord progressions in terminal
✅ Generate MIDI files from chord progressions
✅ Bass line generation (root, root_fifth, walking, swing_walking, stride, boogie)
✅ Drum patterns (rock_beat, shuffle, jazz_swing, kick_only)
✅ Rhythm styles (strumming, fingerpicking, travis, arpeggio, stride, ragtime)
✅ Euclidean rhythms for algorithmic drum patterns
✅ Live visual display - shows current chord, beat, scale fretboard, and chord charts!
✅ Auto-generated melody - improvisation based on scale and style
✅ Guitar fretboard display - shows scale positions for soloing
✅ Chord chart display - shows finger positions for current chord
✅ Strudel export - export to Strudel live coding format
✅ Play backing tracks via FluidSynth (when installed)

Supported Styles: Rock, Blues, Jazz, Folk, Funk, Ska, Reggae, Country, Disco, Motown/Soul, Flamenco, EDM, Trap, Ragtime, Stride, Boogie-Woogie. See MUSIC_STYLES.md for music theory and implementation details.

Why BTML?

Unlike commercial backing track software (iReal Pro, ChordPulse, Band-in-a-Box), BTML is designed for the AI era:

Feature	BTML	Commercial Apps
LLM-friendly	✅ Plain YAML, easily generated by AI	❌ GUI-only, proprietary formats
Version control	✅ Text files, git-friendly	❌ Binary or database formats
Scriptable	✅ CLI-based, pipeable	❌ Manual interaction required
Open source	✅ Fully customizable	❌ Closed source
No subscription	✅ Runs locally with FluidSynth	⚠️ Often subscription-based
Algorithmic rhythms	✅ Euclidean patterns	❌ Fixed presets only

AI Generation Example

Ask any LLM to generate a backing track:

"Create a slow blues in A with walking bass and shuffle drums"

track:
  title: "Slow Blues in A"
  key: A
  tempo: 70
  style: blues

chord_progression:
  pattern: "A7 A7 A7 A7 D7 D7 A7 A7 E7 D7 A7 E7"

bass:
  style: walking

drums:
  style: shuffle

The YAML format is in LLM training data, making generation reliable. No GUI clicking, no manual entry - just pipe the output to a file and play.

Sheet Music to Backing Track in 30 Seconds

With Claude Desktop, you can go from a photo of sheet music to a playing backing track in under 30 seconds:

Take a photo of sheet music, lead sheet, or chord chart
Upload to Claude Desktop with the project instructions
Claude extracts key, tempo, chords, and song structure
Save the BTML and play immediately

📷 Photo of sheet music
       ↓
🤖 Claude Desktop (vision + BTML generation)
       ↓
📄 song.btml
       ↓
🎵 ./backing-tracks play song.btml

No other software offers this workflow. Traditional approaches require:

Sheet music OCR → manual cleanup → DAW import → manual arrangement
Or: manually entering chords into Band-in-a-Box / iReal Pro

With BTML + Claude, the LLM understands musical context, infers missing information, and outputs a ready-to-play backing track. See CLAUDE_DESKTOP_PROJECT.md for setup instructions.

Installation

1. Build the Application

go build -o backing-tracks

2. Install FluidSynth and SoundFont

Ubuntu/Debian:

sudo apt install fluidsynth fluid-soundfont-gm

Arch Linux:

sudo pacman -S fluidsynth soundfont-fluid

macOS:

brew install fluid-synth

Usage

# Play a backing track
./backing-tracks play examples/blues-full.btml

# Export to MIDI file
./backing-tracks export examples/blues-full.btml output.mid

# Export to Strudel (live coding)
./backing-tracks strudel examples/blues-full.btml output.strudel.js

Live Display

During playback, you'll see:

Current chord displayed prominently (with transpose indicator)
Visual metronome with beat indicators
Strum pattern visualization
Scale fretboard showing positions for improvisation
Chord tones fretboard showing all positions for current chord notes
Chord diagrams with finger positions
Track mute status indicators
Progress bar through the progression

Playback Controls:

Key	Action
`Space`	Pause / Resume
`←` / `→`	Jump to previous / next bar
`↑` / `↓`	Transpose up / down by semitone (audio + display)
`Shift+↑` / `Shift+↓`	Speed up / slow down by 5 BPM
`[` / `]`	Move capo down / up (transposes audio + display)
`{` / `}`	Move visual capo down / up (display only, no audio change)
`<` / `>`	Cycle through guitar tunings
`Shift+1-9`	Loop current bar + next N-1 bars (press again to disable)
`Shift+0`	Loop current section (press again to disable)
`1-5`	Toggle track mute (1=drums, 2=bass, 3=chords, 4=melody, 5=fingerstyle)
`;` / `'`	Cycle through fingerstyle patterns
`c`	Toggle chord names display
`e`	Enter lyrics edit mode
`l`	Toggle lyrics display
`m`	Toggle metronome/beat counter
`s`	Toggle strum pattern display
`t`	Toggle inline tablature
`Q` / `Esc`	Quit

Edit Mode (press e to enter):

Edit mode has four focus areas, cycle with Ctrl+F: Lyrics → Form → Sections → Track

Key	Lyrics	Form	Sections	Track
`↑` / `↓`	Previous/next line	Select entry	Select section	Select field
`←` / `→`	Previous/next beat	—	Select chord	Cycle options*
`Shift+←/→`	Move word earlier/later	—	—	—
`Tab` / `Shift+Tab`	Shift all words from here	—	—	Next field
`1-9` / `+`	—	Add section	—	—
`-` / `Del`	Delete word	Remove entry	Delete chord	—
`Shift+↑/↓`	—	Reorder entry	—	—
`r`	—	—	Rename section	—
`Space`	—	—	Commit chord	—
Type	Edit word	—	Edit chord	Edit value
`Ctrl+N`	Create new section (works in any focus)
`Ctrl+S`	Save and exit
`Esc`	Discard and exit

*Fields with cycling options: Style (blues, jazz, rock...), Tuning (standard, drop_d...), Bass (root, walking...), Drums (rock_beat, shuffle...)

BTML File Format

Create .btml files using simple YAML syntax:

track:
  title: "Slow Blues in A (Full Band)"
  key: A
  tempo: 80
  time_signature: 4/4
  style: blues
  capo: 0                # Capo position (0 = no capo)

chord_progression:
  pattern: "A7 A7 A7 A7 D7 D7 A7 A7 E7 D7 A7 E7"
  bars_per_chord: 1
  repeat: 2

rhythm:
  style: shuffle_strum
  swing: 0.6
  instrument: steel_guitar    # Optional: GM instrument name

bass:
  style: swing_walking
  swing: 0.6
  instrument: fingered_bass   # Optional: GM instrument name

drums:
  style: shuffle
  intensity: 0.7

melody:
  enabled: true
  style: simple      # simple, moderate, active
  density: 0.5       # 0.0 to 1.0

Supported Features

Chord Progressions

Basic Pattern:

chord_progression:
  pattern: "C G Am F"
  bars_per_chord: 2
  repeat: 4

Inline Duration Notation:

chord_progression:
  pattern: "C*2 G*1 Am*2 F*1"  # C for 2 bars, G for 1 bar, etc.

Sections & Form (for complex songs):

sections:
  - name: verse
    chord_progression:
      pattern: "C G Am F"
  - name: chorus
    chord_progression:
      pattern: "F G C Am"

form:
  - verse
  - verse
  - chorus
  - verse
  - chorus

Lyrics in Sections (chord-over-lyrics format):

sections:
  - name: verse
    chord_progression:
      pattern: "C G Am F"
    lyrics: |
      C              G
      Here are some words to sing
      Am             F
      This is the melody

Lyrics are displayed during playback when enabled (press l to toggle).

Inline Section Markers (simpler alternative):

chord_progression:
  pattern: "[Intro] Em | [Verse] Am G C D | [Chorus] G D Em C | [Outro] Em"

Section markers like [Verse] or [Chorus] are displayed during playback and can be looped with Shift+0.

Chord Types

Major triads: C, D, E, F, G, A, B
Minor triads: Cm, Dm, Em, Am, etc.
Dominant 7th: C7, D7, E7, A7, etc.
Major 7th: Cmaj7, Dmaj7, Fmaj7, etc.
Minor 7th: Cm7, Dm7, Em7, Am7, etc.
Suspended: Csus4, Dsus2, etc.
Power chords: C5, D5, E5, etc.

Rhythm Styles

Style	Description	Best For
`whole`	One strum per bar	Slow ballads
`half`	Two strums per bar	Ballads
`quarter`	Four strums per bar	Pop, rock
`eighth`	Eight strums per bar	Rock, punk
`sixteenth`	16th note strumming	Funk, disco
`funk_16th`	Funky 16ths with ghost notes	Funk, R&B
`funk_muted`	Heavily muted funk	Funk rock
`strum_down`	Arpeggiated downstrum	Folk
`strum_up_down`	Alternating strums	Pop, rock
`folk`	Bass note + chord pattern	Folk, country
`shuffle_strum`	Triplet shuffle	Blues
`travis`	Travis picking pattern	Country, folk
`fingerpick`	Folk fingerpicking	Singer-songwriter
`fingerpick_slow`	Sparse fingerpicking	Ballads
`pima`	P-i-m-a ascending pattern	Classical, folk
`pima_reverse`	P-a-m-i descending pattern	Classical, ballads
`classical`	P-i-m-i-a-i-m-i full pattern	Classical guitar
`banjo_roll`	Forward roll (T-I-M)	Bluegrass, country
`pinch`	Bass + treble pinch	Folk, country
`dust_in_wind`	Continuous 16th notes	Kansas-style ballads
`landslide`	Fleetwood Mac style	Folk rock
`blackbird`	Walking bass fingerpicking	Beatles-style
`arpeggio_up`	Ascending arpeggio	Classical, ambient
`arpeggio_down`	Descending arpeggio	Classical, ballads
`stride`	Chords on 2 & 4	Ragtime, stride piano
`ragtime`	Stride with syncopation	Ragtime

Instruments

Override the default instrument for any section:

rhythm:
  style: fingerpick
  instrument: nylon_guitar

Category	Instruments
Pianos	`piano`, `electric_piano`, `honky_tonk`, `harpsichord`
Guitars	`nylon_guitar`, `steel_guitar`, `jazz_guitar`, `clean_guitar`, `overdrive`, `distortion`
Bass	`acoustic_bass`, `fingered_bass`, `picked_bass`, `fretless_bass`, `slap_bass`, `synth_bass`
Strings	`violin`, `cello`, `strings`, `contrabass`
Brass	`trumpet`, `trombone`, `brass`, `french_horn`
Woodwinds	`alto_sax`, `tenor_sax`, `clarinet`, `flute`
Organ	`organ`, `church_organ`, `accordion`, `harmonica`

Guitar Tunings

Set alternate tunings for accurate fretboard display:

track:
  title: "Drop D Song"
  tuning: drop_d

Tuning	Notes	Use Case
`standard`	E A D G B e	Default
`drop_d`	D A D G B e	Foo Fighters, Rage Against the Machine
`drop_c`	C G C F A d	Heavy metal
`d_standard`	D G C F A d	Slightly lower, Nirvana
`eb_standard`	Eb Ab Db Gb Bb eb	Half step down, SRV, GnR
`open_e`	E B E G# B e	Slide blues, Black Crowes
`open_d`	D A D F# A d	Slide, Joni Mitchell
`open_g`	D G D G B d	Keith Richards, Rolling Stones
`open_a`	E A E A C# e	Slide blues
`dadgad`	D A D G A d	Celtic, Pierre Bensusan
`open_c`	C G C G C e	Devin Townsend

Bass Styles

Style	Description	Best For
`root`	Root notes on downbeats	Simple accompaniment
`root_fifth`	Root on 1, fifth on 3	Folk, country, rock
`walking`	Root, 3rd, 5th, 7th pattern	Jazz
`swing_walking`	Swung walking bass	Jazz, blues
`stride`	Low bass on 1 & 3	Ragtime, stride piano
`boogie`	Driving eighth note pattern	Boogie-woogie, rock & roll

Drum Patterns

Preset Styles:

Style	Description
`rock_beat`	Kick 1,3 / Snare 2,4 / 8th hihat
`shuffle`	Blues shuffle with triplet feel
`jazz_swing`	Swinging ride with sparse kick/snare
`kick_only`	Just kick drum (for stripped-down tracks)

Euclidean Rhythms:

drums:
  kick:
    euclidean: { hits: 5, steps: 8, rotation: 0 }
  snare:
    euclidean: { hits: 3, steps: 8, rotation: 2 }
  hihat:
    euclidean: { hits: 7, steps: 8, rotation: 0 }

Melody Generation

Auto-generate an improvisation track:

melody:
  enabled: true
  style: simple      # simple (half notes), moderate (quarters), active (eighths)
  density: 0.5       # 0.0 to 1.0 - how many notes to play

The melody uses scale-appropriate notes based on the track style:

Blues → Blues scale
Jazz → Dorian/Mixolydian modes
Rock → Pentatonic minor
Folk/Pop → Natural major/minor

Scale Override

Force a specific scale instead of auto-detection:

scale:
  type: blues  # pentatonic_minor, pentatonic_major, blues, dorian, mixolydian, natural_minor, natural_major

Example Tracks

The examples/ directory contains many demo tracks:

Blues Styles

File	Description
`blues-full.btml`	Full band blues with swing walking bass
`blues-delta.btml`	Raw, sparse Delta blues (72 BPM)
`blues-chicago.btml`	Electric Chicago shuffle (116 BPM)
`blues-texas.btml`	Clean, jazzy Texas blues (126 BPM)
`blues-jump.btml`	Uptempo jump blues (168 BPM)
`blues-slow.btml`	Soulful slow blues (58 BPM)
`blues-west-coast.btml`	Jazzy West Coast blues (96 BPM)
`blues-boogie.btml`	John Lee Hooker style one-chord boogie

Fingerpicking

File	Description
`fingerpick-travis.btml`	Travis picking in G (country/folk)
`fingerpick-folk.btml`	Classic folk fingerpicking
`fingerpick-ballad.btml`	Slow ballad fingerpicking
`fingerpick-arpeggio.btml`	Classical ascending arpeggios
`fingerpick-spanish.btml`	Spanish romance style
`fingerpick-songwriter.btml`	Singer-songwriter style

Ragtime & Boogie

File	Description
`ragtime.btml`	Classic stride piano ragtime
`boogie-woogie.btml`	Driving boogie-woogie piano
`rock-n-roll-piano.btml`	50s rock & roll (Jerry Lee Lewis style)

Other Styles

File	Description
`pop-full.btml`	Pop with bass & drums
`rock-euclidean.btml`	Rock with Euclidean drum patterns
`jazz-swing.btml`	Jazz II-V-I with walking bass
`little-wing.btml`	Ballad in Em

Try them:

./backing-tracks play examples/blues-chicago.btml
./backing-tracks play examples/fingerpick-travis.btml
./backing-tracks play examples/ragtime.btml
./backing-tracks play examples/rock-n-roll-piano.btml

Project Structure

backing-tracks/
├── main.go              # CLI entry point
├── parser/
│   └── parser.go        # BTML YAML parser
├── midi/
│   ├── generator.go     # MIDI file generation
│   ├── bass.go          # Bass pattern generator
│   ├── drums.go         # Drum pattern generator
│   ├── rhythm.go        # Chord rhythm patterns
│   └── melody.go        # Melody generation
├── player/
│   └── fluidsynth.go    # FluidSynth integration
├── display/
│   ├── terminal.go      # Terminal display formatting
│   ├── live.go          # Real-time playback display
│   ├── fretboard.go     # Guitar fretboard visualization
│   └── chords.go        # Chord diagram display
├── theory/
│   └── theory.go        # Music theory (scales, keys)
├── strudel/
│   └── generator.go     # Strudel export
├── examples/            # Example BTML files
└── README.md

Roadmap

v0.1: ✅ Basic chord progression playback
v0.2: ✅ Bass line generation
v0.3: ✅ Drum patterns (presets + Euclidean rhythms)
v0.4: ✅ Live visual display with chord and beat tracking
v0.5: ✅ Scale display, chord charts, melody generation, Strudel export
v0.6: ✅ 16th note rhythms, Bubbletea TUI
v0.7: ✅ Full TUI edit mode (lyrics, form, sections, track properties)
v0.8: Mini-notation parser (Strudel-inspired)
v0.9: LLM integration for generating BTML from songs

Dependencies

Go Libraries:

gopkg.in/yaml.v3 - YAML parsing
gitlab.com/gomidi/midi/v2 - MIDI file generation
github.com/charmbracelet/bubbletea - Terminal UI framework
github.com/charmbracelet/lipgloss - Terminal styling

External:

FluidSynth - Audio synthesis

Troubleshooting

"fluidsynth not found"

Install FluidSynth: sudo apt install fluidsynth fluid-soundfont-gm

"no SoundFont (.sf2) file found"

Install a SoundFont package: sudo apt install fluid-soundfont-gm

No audio output

Check your system audio settings and ensure FluidSynth can access your audio device.

License

MIT

Contributing

Contributions welcome! See:

BTML_MANUAL.md for the full BTML specification
MUSIC_STYLES.md for music theory and style implementation details
CLAUDE.md for development guidelines

What's New

v0.7 (Current)

✅ Full edit mode: Edit lyrics, form, sections, and track properties in the TUI
✅ Track property editor: Edit title, key, tempo, style, tuning, bass, drums directly
✅ Cycle through options: Use ←/→ to scroll through style, tuning, bass, and drums presets
✅ Form editor: Add, remove, and reorder sections in the song structure
✅ Sections editor: Edit chord progressions, rename sections, create new sections
✅ Lyrics timing editor: Move words between beats with Shift+←/→

v0.6

✅ Lyrics support: Add chord-over-lyrics in sections, display during playback (l to toggle)
✅ Real-time playback controls: Pause/resume (space), seek (←/→)
✅ Transpose controls: Shift song up/down by semitones (↑/↓)
✅ Capo support: Set capo in BTML file or adjust live with [/] keys
✅ Instrument selection: Choose GM instruments per section (nylon_guitar, slap_bass, etc.)
✅ Sections & Form: Define verse/chorus/bridge sections, specify song structure
✅ Guitar tunings: Drop D, Open E, Open G, DADGAD, and more
✅ Track mute controls: Mute individual tracks with keys 1-4
✅ Chord tones fretboard: Shows all positions for current chord notes
✅ Synced audio & display: Controls affect both sound and visuals
✅ Multi-chord bar display: Shows "Am7 → Am" for half-bar chords
✅ Pattern list support: Chord patterns can be YAML lists
✅ 16th note rhythm styles: sixteenth, funk_16th, funk_muted
✅ Bubbletea TUI: Proper terminal UI with Lipgloss styling
✅ Beat subdivision display: Shows "1 e + a 2 e + a..." for 16th notes
✅ TTY detection: Falls back to legacy display in non-terminal environments

v0.5

✅ Guitar fretboard display showing scale positions for improvisation
✅ Chord chart display with finger positions (open + barre voicings)
✅ Auto-generated melody track based on scale and chord tones
✅ Smart scale detection based on track style (blues, jazz, rock, etc.)
✅ Strudel export for live coding
✅ New rhythm styles: stride, ragtime, fingerpicking variants
✅ New bass styles: stride, boogie
✅ Many new examples: blues styles, fingerpicking, ragtime, boogie-woogie

v0.4

✅ Live visual display during playback
✅ Inline duration notation for chords
✅ Karaoke-style scrolling display with lyrics support

v0.3

✅ Bass line generation (4 styles)
✅ Drum patterns (3 presets + Euclidean)
✅ Swing feel for bass

v0.2

✅ Bass line generation (initial)

v0.1

✅ Chord progression playback
✅ FluidSynth integration

Name		Name	Last commit message	Last commit date
Latest commit History 61 Commits
.claude/skills/btml-generation		.claude/skills/btml-generation
display		display
docs		docs
examples		examples
midi		midi
parser		parser
player		player
soundfonts		soundfonts
strudel		strudel
theory		theory
.gitignore		.gitignore
CLAUDE.md		CLAUDE.md
LICENSE		LICENSE
README.md		README.md
go.mod		go.mod
go.sum		go.sum
main.go		main.go
screenshot-player.png		screenshot-player.png

License

ako/backing-tracks

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Backing Tracks - v0.7

What Works

Why BTML?

AI Generation Example

Sheet Music to Backing Track in 30 Seconds

Installation

1. Build the Application

2. Install FluidSynth and SoundFont

Usage

Live Display

BTML File Format

Supported Features

Chord Progressions

Chord Types

Rhythm Styles

Instruments

Guitar Tunings

Bass Styles

Drum Patterns

Melody Generation

Scale Override

Example Tracks

Blues Styles

Fingerpicking

Ragtime & Boogie

Other Styles

Project Structure

Roadmap

Dependencies

Troubleshooting

"fluidsynth not found"

"no SoundFont (.sf2) file found"

No audio output

License

Contributing

What's New

About

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