Isabelle van Keulen (born 16 December 1966) is a Dutch violinist and violist, performing principally as a chamber musician but also as a concert violist. She founded the Isos Quartet in 1995. For more
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
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xd7d0bfab25b47df4685c0fd2a0d7f2159d33c6e3d3039a2bd9b8ef429a885775. Chain 2 (Bitcoin): anchored in block 953407 (2026-06-12T19:24:56Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/44a1db56-d04f-46ef-be60-22a78d692f12.json and https://artists.proofprofile.net/proofs/artist/44a1db56-d04f-46ef-be60-22a78d692f12.ots, the client at https://opentimestamps.org runs `ots verify -f record.json proof.ots`.
Haydn: Violin Concerto No. 1 / Mozart: Violin Concerto No. 2
Saint-Saëns: Violin Concerto No. 3 / Vieuxtemps: Violin Concerto No. 5 / Ysaÿe: Solo Violin Sonata No. 5
Debussy: Violin Sonata in G Minor, CD 148 / Fauré: Violin Sonata No. 1 in A Major, Op. 13 / Poulenc: Violin Sonata, FP 119
Brahms - Dietrich - Clara Schumann (Sonatas for Violin and Piano)
Grieg, Elgar and Sibelius: Music for Violin and Piano
Sharon Kam Portrait - Virtuose Klarinettenmusik
Prokofiev: Violin Concerto No. 1 - Walton: Viola Concerto - Vaughan Williams: The Lark Ascending
Quintet for Clarinet, Two Violins, Viola and Violoncello in A Major, K. 581: I. Allegro
Mozart: Clarinet Concerto, K. 622 & Clarinet Quintet, K. 581
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
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x0ffd07457e845b7233c3076213e5bc961248d47dac20fd50d6c9a5ac77baff8e. Chain 2 (Bitcoin): anchored in block 957118 (2026-07-08T03:20:19Z), 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 at https://artists.proofprofile.net/api/v1/bot/ots/verify/track/DES380020201 — a six-check JSON result.
Quintet for Clarinet, Two Violins, Viola and Violoncello in A Major, K. 581: II. Larghetto
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0xd93d09bdb4be88d46492193d18d85e22e9cf512a9e16311f873a678e02dc6375. Chain 2 (Bitcoin): anchored in block 960427 (2026-07-31T15:59:18Z), 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 at https://artists.proofprofile.net/api/v1/bot/ots/verify/track/DES380020202 — a six-check JSON result.
Quintet for Clarinet, Two Violins, Viola and Violoncello in A Major, K. 581: IV. Allegretto con variazioni
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x6b598d6f4371c31f42b36dd4b4b71c6133206388c89d69774b2ba638f75df468. Chain 2 (Bitcoin): anchored in block 957118 (2026-07-08T03:20:19Z), 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 at https://artists.proofprofile.net/api/v1/bot/ots/verify/track/DES380020204 — a six-check JSON result.