What is btml-generation?

A tool that writes BTML files, a YAML-based format for guitar backing tracks. These files can describe chords, rhythm, bass, drums, melody, key, tempo, tuning, and capo settings for use with the backing-tracks command-line tool.

Use it to create guitar practice tracks with chord progressions, rhythm patterns, bass lines, drum styles, optional melodies, and scales.

It turns a practice idea into a structured backing-track file instead of requiring the player to describe every musical part manually.

How ako/backing-tracks configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to ako/backing-tracks. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/ako/backing-tracks/main/.claude/skills/btml-generation/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/ako/backing-tracks

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/ako/backing-tracks/btml-generation/github.svg)](https://agentmods.dev/skills/ako/backing-tracks/btml-generation)

Your own site

<a href="https://agentmods.dev/skills/ako/backing-tracks/btml-generation"><img src="https://agentmods.dev/badge/skills/ako/backing-tracks/btml-generation/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/ako/backing-tracks/btml-generation"><img src="https://agentmods.dev/badge/skills/ako/backing-tracks/btml-generation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 13 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,170 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00013	$0.02170
Opus 5.5	$0.00005	$0.00868
Sonnet 5.5	$0.00003	$0.00434
Haiku 4.5	$0.00001	$0.00217

Measured 2mo ago against content hash 3778dc03749b, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

btml-generation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/btml-generation/SKILL.md · 316 lines

How it starts

The opening of the file, as written. The whole thing — 316 lines — stays where its author put it; the contents beside it link to each section on GitHub.

BTML Generation Skill

Generate BTML (Backing Track Markup Language) files for guitar practice backing tracks.

What is BTML?

BTML is a YAML-based notation for defining complete backing tracks with chords, rhythm patterns, bass lines, drums, and melody. Files use the .btml extension and are played with the backing-tracks CLI.

File Structure

track:
  title: "Song Name"
  key: C                    # Musical key (C, G, Am, F#, Bb, etc.)
  tempo: 120                # BPM
  time_signature: 4/4
  style: rock               # Genre hint
  tuning: standard          # Guitar tuning (optional)
  capo: 0                   # Capo position (optional)

chord_progression:
  pattern: "C G Am F"       # Space-separated chord symbols
  bars_per_chord: 1
  repeat: 4

rhythm:
  style: eighth             # Chord rhythm style

bass:
  style: root_fifth

drums:
  style: rock_beat
  intensity: 0.7

melody:
  enabled: true
  style: moderate
  density: 0.5

scale:
  type: pentatonic_minor

Chord Symbols

Symbol	Type
`C`, `G`, `D`	Major triad
`Am`, `Em`, `Dm`	Minor triad
`A7`, `E7`, `D7`	Dominant 7th
`Cmaj7`, `Gmaj7`	Major 7th
`Am7`, `Em7`	Minor 7th
`E9`, `A9`	Dominant 9th
`E5`, `A5`	Power chord
`Asus4`, `Dsus2`	Suspended
`Bb`, `F#`, `Eb`	Accidentals
`Am/G`, `C/E`	Slash chords (bass note)
`C2`, `Am0.5`	Duration override (bars)

Genre Guidelines

Blues

track:
  key: A
  tempo: 80
  style: blues
chord_progression:
  pattern: "A7 A7 A7 A7 D7 D7 A7 A7 E7 D7 A7 E7"  # 12-bar blues
rhythm:
  style: shuffle_strum
  swing: 0.67
bass:
  style: walking
  swing: 0.67
drums:
  style: blues_shuffle
  intensity: 0.7
melody:
  style: blues_head
scale:
  type: blues

Jazz

track:
  key: C
  tempo: 140
  style: jazz
chord_progression:
  pattern: "Dm7 G7 Cmaj7 Cmaj7"  # II-V-I
rhythm:
  style: stride
  swing: 0.67
bass:
  style: walking
drums:
  style: jazz_swing
  intensity: 0.6

Read the full file on GitHub · 316 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 316 lines · 13 tokens per session scan A 3778dc03749b

Subscribe to this mod's changes

btml-generation is a skill published in the GitHub repository ako/backing-tracks (20 stars, last pushed 10mo ago), licensed MIT. It adds 13 tokens to every session and 2,170 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Creative and media

btml-generation next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
btml-generationako/backing-tracks	Skill	20	10mo ago	MIT	A	13	Claude Code
imagegenopenai/codex	Skill	135k	today	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	100k	today	Apache-2.0	A	19	Claude Code
browser-automationopenclaw/openclaw	Skill	394k	today	MIT	A	36	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	5d ago	MIT	A	200	Claude Code, Codex
next-cache-components-adoptionvercel/next.js	Skill	143k	today	MIT	A	95	Claude Code
systematic-debuggingobra/superpowers	Skill	316k	8d ago	MIT	A	21	Claude Code

backing-tracks: Skill for Claude Code