transpose

name	transpose
description	Transposes a chord by a named musical interval (e.g. Cmaj7 up a perfect fourth = Fmaj7). Calls the deterministic `domain.transposeChord` closure via the `ga_dsl_eval` MCP tool — never recall transpositions from training data, since LLMs commonly produce wrong enharmonics for less-common keys (Db major vs C# major).
triggers	["transpose","move this chord","shift this chord","up a","down a","in the key of","change the key"]
license	internal
compatibility	{"agent-framework":">=1.0.0-preview","microsoft-extensions-ai":">=10.5.1"}
metadata	{"authoring-style":"tool-driven","origin":"graduated 2026-05-06 — first canary for ga_dsl_eval (Phase 2 of skills-orchestration plan)","evidence-kinds":["tool_call"]}
allowed-tools	["ga_dsl_eval"]
last_verified	"2026-05-06T00:00:00.000Z"

Transpose a Chord

When a user asks to transpose a chord by an interval (or to move it into a different key), call ga_dsl_eval with closure name domain.transposeChord. Do NOT compute the transposition mentally — for less-common keys (Gb major, C# minor) the LLM will confidently flip enharmonics and produce wrong spellings.

Why this skill uses ga_dsl_eval (not a keyhole tool)

This is the first canary for the DSL-eval pattern. Instead of one MCP tool per gap, we call the existing domain.transposeChord closure through the universal ga_dsl_eval entry point. The closure is registered in GaClosureRegistry and exposed only because its category is Domain (per docs/contracts/2026-05-06-ga-dsl-eval-contract.md v0.1).

Calling the tool

Method: ga_dsl_eval

Args (flat key-value, all values as strings):

• closureName = "domain.transposeChord"
• args.symbol — the chord symbol, e.g. "Cmaj7", "F#m", "Bb7".
• args.semitones — integer string. Positive = up, negative = down. Convert from interval names using the table below.

Example invocation:

ga_dsl_eval(closureName: "domain.transposeChord",
            args: { "symbol": "Cmaj7", "semitones": "5" })

Returns a DslEvalResult. Read Result for the new chord symbol (e.g. "Fmaj7"); on failure, read Error.Code and Error.Message.

Interval → semitones table

Use this to convert the user's phrasing into the semitones arg. Direction "up" = positive; "down" = negative.

Interval	Semitones	Common phrasings
unison / P1	0	"no change", "same root"
minor 2nd / m2 / half step	1	"up a half step", "by a semitone"
major 2nd / M2 / whole step	2	"up a whole step", "by two semitones"
minor 3rd / m3	3	"up a minor third", "by three semitones"
major 3rd / M3	4	"up a major third"
perfect 4th / P4	5	"up a perfect fourth", "by a fourth"
tritone / TT / dim 5 / aug 4	6	"by a tritone"
perfect 5th / P5	7	"up a perfect fifth", "by a fifth"
minor 6th / m6	8	"up a minor sixth"
major 6th / M6	9	"up a major sixth"
minor 7th / m7	10	"up a minor seventh"
major 7th / M7	11	"up a major seventh"
octave / P8	12	"up an octave"

Direction "down" means negative semitones. "Down a minor third" → semitones = -3.

Mapping user phrasings

• "Transpose Cmaj7 up a perfect fourth" → args = { "symbol": "Cmaj7", "semitones": "5" }
• "Move this F chord down a minor third" → args = { "symbol": "F", "semitones": "-3" }
• "What's Dm7 up a whole step?" → args = { "symbol": "Dm7", "semitones": "2" }
• "Cmaj7 in the key of G" — G is up a perfect fifth from C, so args = { "symbol": "Cmaj7", "semitones": "7" }. If ambiguous (could go down), surface the assumption.

Phrasing the answer

Lead with the result. Cite the interval and direction so the user can verify:

Cmaj7 up a perfect fourth = Fmaj7 (interval = +5 semitones).

If the closure returns an error (Error non-null), surface the message verbatim and ask the user to clarify the chord name. Common cases:

• closure-runtime-error with a ParseError — chord symbol couldn't be parsed (typo, unsupported quality, etc.)
• arg-coerce-failed on semitones — should not happen if you wrote a valid integer string

When to refuse / clarify

• "Transpose this whole progression" — call this skill once per chord, OR ask the user to list the chords. Bulk-transposition is roadmap.
• Keys named ambiguously ("in C" — major or minor?) — pick the same mode as the source chord, OR ask.
• Slash chords (e.g. C/E up a fifth) — the closure may not preserve the bass note correctly; warn the user that the bass note in the answer may need verification.

Out of scope

• Whole-progression transposition — separate call per chord; the closure is single-chord.
• Capo translation — separate skill (BACKLOG #139 gap, not yet shipped).
• Tuning-aware transposition (DADGAD, drop-D shape adjustments) — separate skill.

Cross-reference

• MCP tool surface: ga_dsl_eval in Common/GA.Business.ML/Agents/Mcp/DslEvalMcpTools.cs
• Closure: domain.transposeChord in Common/GA.Business.DSL/Closures/BuiltinClosures/DomainClosures.fs
• Contract: docs/contracts/2026-05-06-ga-dsl-eval-contract.md (v0.1)
• Plan: docs/plans/2026-05-06-skills-orchestration-architecture.md (Phase 2 canary)