{"uid":"cap_NFKDtYiQ6E25xYuqSa8ln","slug":"music-theory-note-to-frequency-converter-3caa6314","name":"Music Theory Note-to-Frequency Converter","description":"Note name (C#4, Bb3) or MIDI number to MIDI, frequency in Hz and wavelength, with adjustable A4 reference pitch.","url":"https://music-theory.x402tookit.com/note-freq?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":["note"],"properties":{"a4":{"type":"number","description":"Reference pitch for A4 in Hz, 400 to 480 (default 440; baroque 415, Verdi 432)"},"note":{"type":"string","description":"Note name with octave (A4, C#5, Eb3) or a MIDI number 0 to 127"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"a4Hz":{"type":["null","number"]},"asOf":{"type":["null","string"]},"midi":{"type":["null","number"]},"note":{"type":["null","string"]},"source":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"pitchClass":{"type":["null","number"]},"frequencyHz":{"type":["null","number"]},"wavelengthCm":{"type":["null","number"]},"wavelengthNote":{"type":["null","string"]},"enharmonicNames":{"type":["array","null"],"items":{"type":"string"}},"octaveConvention":{"type":["null","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_9rR4QCGk8YLPT1ghgrD6s","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":"Converts a note name (e.g. C#4, Bb3) or MIDI number to its MIDI value, frequency in Hz, and wavelength in cm, with an adjustable A4 reference pitch.","exampleAgentPrompt":"What is the frequency in Hz and MIDI number for C#4, using a 432 Hz A4 reference pitch?","exampleUseCases":[{"title":"Synthesizer patch frequency lookup","prompt":"I'm programming a synth patch and need the exact frequency in Hz and MIDI number for Bb3 using standard 440 Hz tuning — can you look that up?"},{"title":"Baroque tuning instrument check","prompt":"What's the frequency and wavelength of A4 when the reference pitch is set to baroque tuning at 415 Hz?"},{"title":"MIDI number to note properties","prompt":"I have MIDI note 60 — can you tell me the note name, frequency in Hz, and wavelength at standard 440 A4 tuning?"}],"resultDescription":"Returns the note name, MIDI number, pitch class, frequency in Hz, wavelength in cm, enharmonic equivalents, the A4 reference Hz used, and the octave convention, along with a summary and optional degraded/disclaimer flags.","failureModes":["Invalid note name format (e.g. missing octave number) returns an error","MIDI number outside 0–127 range is rejected","A4 reference pitch outside 400–480 Hz range is invalid","Malformed query parameter causes a bad request response","Missing required 'note' parameter returns an error"],"whenToPreferThis":"Use this endpoint when you need to convert a note name or MIDI number to its exact frequency, MIDI value, and wavelength — especially when non-standard tuning (baroque 415, Verdi 432, custom A4) is required. Prefer this over generic music APIs when precise acoustic properties and enharmonic spellings are needed for a specific note.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:14:23.982Z","isFirstParty":false,"canonicalSlug":"music-theory-note-to-frequency-converter-3caa6314"}