Opus Cuatro
type: MusicGroup
genre: folklore argentino
genre: tango
description: Opus Cuatro are an Argentine folk vocal quartet founded in La Plata in 1968. The group debuted on 10 July 1968 and become one of the most important vocal groups in Latin America, staying active since
popularity: 12
followers: 2053
additional property: CopyrightID
additional property: CopyrightChainExplorerURL
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  value: https://explorer.copyrightchains.com/tx/0xf2c17876fdbf15346469ff330112d23d9eba352761b3365ef35598cb866a9020
additional property: OTSHash
additional property: OTSBitcoinBlock
  type: PropertyValue
  value: 953778
additional property: OTSBitcoinBlockVerifyURL
  type: PropertyValue
  value: https://blockstream.info/api/block-height/953778
additional property: OTSProofURL
  type: PropertyValue
  value: https://artists.proofprofile.net/proofs/artist/a91e4c00-bf52-4ed1-ade9-47778e5f9f7c.ots
additional property: OTSRecordURL
  type: PropertyValue
  value: https://artists.proofprofile.net/proofs/artist/a91e4c00-bf52-4ed1-ade9-47778e5f9f7c.json
additional property: OTSVerificationAPI
  type: PropertyValue
  value: https://artists.proofprofile.net/api/v1/bot/ots/verify/artist/a91e4c00-bf52-4ed1-ade9-47778e5f9f7c
additional property: OTSTimestamp
  type: PropertyValue
  value: 2026-06-15T11:57:35Z
additional property: OTSCanonicalRecord
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additional property: OTSVerifyInstructions
  type: PropertyValue
  value: 1. Compute SHA-256 of OTSCanonicalRecord value → must equal OTSHash 2. Open OTSProofURL → extract Bitcoin block number → must equal OTSBitcoinBlock 3. GET OTSBitcoinBlockVerifyURL → returns the Bitcoin block hash at height OTSBitcoinBlock; GET https://blockstream.info/api/block/{that hash} → its timestamp must match OTSTimestamp 4. Read CopyrightID inside OTSCanonicalRecord → must equal the CopyrightID above 5. GET OTSVerificationAPI → pre-computed 6-check result from server 6. If all match: this entity was registered on CopyrightChains at OTSTimestamp, independently verifiable on Bitcoin Note: an OTS proof may carry multiple Bitcoin attestations; OTSBitcoinBlock is the earliest confirmed one — a later attestation inside the proof corroborates it and is not a mismatch
subject of: OpenTimestamps Proof of Existence
  type: DigitalDocument
  encoding format: application/vnd.opentimestamps.ots
  description: Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xf2c17876fdbf15346469ff330112d23d9eba352761b3365ef35598cb866a9020. Chain 2 (Bitcoin): anchored in block 953778 (2026-06-15T11:57:35Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/a91e4c00-bf52-4ed1-ade9-47778e5f9f7c.json and https://artists.proofprofile.net/proofs/artist/a91e4c00-bf52-4ed1-ade9-47778e5f9f7c.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).
  date published: 2026-06-15T11:57:35Z
  text: {"copyright_id":"0xf2c17876fdbf15346469ff330112d23d9eba352761b3365ef35598cb866a9020","name":"Opus Cuatro","registered_at":"2026-06-14T22:12:33Z","symbol":"NIM0592328","token_address":"0x77d1e75208e423053c28df9af13793a2d7f0cfbf","type":"artist","uuid":"a91e4c00-bf52-4ed1-ade9-47778e5f9f7c"}
album: América!
  type: MusicAlbum
  date published: 1970-05-02
album: América!
  type: MusicAlbum
  date published: 1970-05-02
album: Con América en la Sangre
  type: MusicAlbum
  date published: 1971-08-01
album: Si Somos Americanos...
  type: MusicAlbum
  date published: 1973-06-01
album: Op. IV ~nº4
  type: MusicAlbum
  date published: 1976
album: Opus Cuatro
  type: MusicAlbum
  date published: 1980
album: Jazz Spirituals Musicals
  type: MusicAlbum
  date published: 1980-01-01
album: Jazz Spirituals Musicals
  type: MusicAlbum
  date published: 1980-01-01
album: Canta Con los Coros Argentinos
  type: MusicAlbum
  date published: 1980-01-01
album: Un Nuevo Tiempo
  type: MusicAlbum
  date published: 1987
album: Por Amor
  type: MusicAlbum
  date published: 1992
album: Por Amor
  type: MusicAlbum
  date published: 1992-01-01
album: Milagro de Amor
  type: MusicAlbum
  date published: 1998
album: Milagro de Amor
  type: MusicAlbum
  date published: 1998-01-01
album: Europa en Vivo
  type: MusicAlbum
  date published: 2000-01-01
album: Tangos Valses y Milongas
  type: MusicAlbum
  date published: 2006-09-25
album: Militantes de la Vida
  type: MusicAlbum
  date published: 2007-03-02
  track: Por Qué Cantamos
    type: MusicRecording
    duration: PT3M57S
    duration ms: 237026
    explicit: false
    by artist: Opus Cuatro
    in album: Militantes de la Vida
      type: MusicAlbum
      date published: 2007-03-02
    genre: folklore argentino
    genre: tango
    isrc code: ARG601012626
    additional property: CopyrightID
    additional property: CopyrightStatus
      type: PropertyValue
      value: registered
    additional property: CopyrightRegisteredAt
      type: PropertyValue
      value: 2026-07-20T09:02:48+00:00
    additional property: CopyrightChainExplorerURL
      type: PropertyValue
      value: https://explorer.copyrightchains.com/tx/0x093c797ed44e166318a183690296103b08a411005a469ab17ad540e6f3a2eb8d
    additional property: OTSHash
    additional property: OTSBitcoinBlock
      type: PropertyValue
      value: 958857
    additional property: OTSBitcoinBlockVerifyURL
      type: PropertyValue
      value: https://blockstream.info/api/block-height/958857
    additional property: OTSVerificationAPI
      type: PropertyValue
      value: https://artists.proofprofile.net/api/v1/bot/ots/verify/track/ARG601012626
    additional property: OTSTimestamp
      type: PropertyValue
      value: 2026-07-20T09:45:25Z
    additional property: OTSVerifyInstructions
      type: PropertyValue
      value: 1. Confirm isrcCode identifies the recording in the pre-2022 source corpus and cc-db-prod record 2. GET OTSVerificationAPI → server-side canonical-record, hash, and attestation checks must pass 3. GET OTSBitcoinBlockVerifyURL → returns the Bitcoin block hash at height OTSBitcoinBlock; GET https://blockstream.info/api/block/{that hash} → its timestamp must match OTSTimestamp 4. Confirm CopyrightID is the CopyrightChains transaction hash 5. If all match: the cc-db-prod record is independently anchored on Bitcoin at OTSTimestamp Note: an OTS proof may carry multiple Bitcoin attestations; OTSBitcoinBlock is the earliest confirmed one — a later attestation inside the proof corroborates it and is not a mismatch
    subject of: OpenTimestamps Proof of Existence
      type: DigitalDocument
      encoding format: application/vnd.opentimestamps.ots
      description: Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x093c797ed44e166318a183690296103b08a411005a469ab17ad540e6f3a2eb8d. Chain 2 (Bitcoin): anchored in block 958857 (2026-07-20T09:45:25Z), registered by our registry partner. The server verifies the private canonical record against OTSHash without exposing internal provider keys. Confirm the public ISRC, CopyrightID, and Bitcoin evidence via https://artists.proofprofile.net/api/v1/bot/ots/verify/track/ARG601012626.
      date published: 2026-07-20T09:45:25Z
    audio: Por Qué Cantamos
      type: AudioObject
      additional property: Tempo (BPM)
        type: PropertyValue
        value: 121.372
      additional property: Musical Key
        type: PropertyValue
        value: 5
      additional property: Mode (Major/Minor)
        type: PropertyValue
        value: 1
      additional property: Time Signature
        type: PropertyValue
        value: 4
      additional property: Danceability
        type: PropertyValue
        value: 0.479
      additional property: Energy
        type: PropertyValue
        value: 0.291
      additional property: Speechiness
        type: PropertyValue
        value: 0.053
      additional property: Acousticness
        type: PropertyValue
        value: 0.806
      additional property: Instrumentalness
        type: PropertyValue
        value: 0
      additional property: Liveness
        type: PropertyValue
        value: 0.222
      additional property: Valence (Positivity)
        type: PropertyValue
        value: 0.317
      additional property: Loudness (dB)
        type: PropertyValue
        value: -15.263
      additional property: Key Name
        type: PropertyValue
        value: F
      additional property: Mode Name
        type: PropertyValue
        value: Major
album: No Dejes de Cantar
  type: MusicAlbum
  date published: 2007-03-02
album: No Dejes de Cantar
  type: MusicAlbum
  date published: 2008
album: Militantes de la Vida
  type: MusicAlbum
  date published: 2008
album: Tangos Valses y Milongas
  type: MusicAlbum
  date published: 2008
album: Sinfonico
  type: MusicAlbum
  date published: 2010-10-10
album: Sinfonico
  type: MusicAlbum
  date published: 2010-10-10