{"uid":"cap_4GENlvSwl1qqs8X6ZJB1V","slug":"music-theory-chord-progression-transposer-af30dffb","name":"Music Theory – Chord Progression Transposer","description":"Transpose a chord progression by semitones or from one key to another, with spelling that fits the target key.","url":"https://music-theory.x402tookit.com/transpose?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["progression"],"properties":{"toKey":{"type":"string","description":"Target key, e.g. G or Em; the shift is the upward distance between tonics"},"prefer":{"type":"string","description":"sharps or flats to force the spelling of out-of-key chords"},"fromKey":{"type":"string","description":"Original key, e.g. C or Am"},"semitones":{"type":"integer","description":"Shift -24 to 24 semitones (use this, or fromKey and toKey)"},"progression":{"type":"string","description":"Chords separated by spaces, commas or bars: C Am F G7"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"toKey":{"type":["null","string"]},"chords":{"type":["array","null"],"items":{"type":"object","properties":{"input":{"type":["null","string"]},"output":{"type":["null","string"]}}}},"source":{"type":["null","string"]},"fromKey":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"semitones":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"transposed":{"type":["array","null"],"items":{"type":"string"}}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_naMTSUMlednQz4YT1Q4N4","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Transposes a chord progression by a given number of semitones or between two keys, returning correctly spelled output chords for the target key.","exampleAgentPrompt":"Can you transpose the chord progression C Am F G7 from C major to G major and make sure the chords are spelled correctly for the new key?","exampleUseCases":[{"title":"Singer's key adjustment","prompt":"The song is in C major with chords C Am F G, but my vocalist needs it 3 semitones higher — can you transpose the whole progression for me?"},{"title":"Jazz chart transposition for horn","prompt":"I've got a jazz progression Cmaj7 Am7 Dm7 G7 written for piano in C. Can you transpose it to Bb major so a tenor sax player can read it in concert pitch?"},{"title":"Capo-friendly guitar key change","prompt":"I want to play Am G F E on guitar but my capo is on fret 2 — what does the progression become if I shift everything down 2 semitones, spelled with flats?"}],"resultDescription":"Returns a list of transposed chord names (one per input chord), the detected or specified source key, the target key, the semitone distance applied, a summary string, and per-chord input-to-output mappings. May also include spelling rationale and a disclaimer if any chords could not be resolved.","failureModes":["Missing required 'progression' parameter returns an error","Ambiguous or unrecognised chord symbols may result in null output entries or a 'notChecked' list","Providing both 'semitones' and 'fromKey'/'toKey' may cause conflict; only one method should be used","Out-of-range semitone values (beyond ±24) are rejected","Misspelled key names (e.g. 'Csharp' instead of 'C#') may fail to parse"],"whenToPreferThis":"Use this endpoint when you need to move an entire chord progression to a new key with musically correct chord spelling — e.g. Bb instead of A# in flat keys. Prefer it over manual interval arithmetic when key context matters for enharmonic spelling correctness. Ideal for song arrangement, vocal range matching, instrument transposition, and capo calculations.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:08:11.103Z","isFirstParty":false,"canonicalSlug":"music-theory-chord-progression-transposer-af30dffb"}