thumb|Mieczysław Horszowski in 1990 Mieczysław Horszowski (June 23, 1892May 22, 1993) was a Polish and American pianist who had one of the longest careers in the history of the performing arts. Life
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
Dual-chain trust anchor. Chain 1 (CopyrightChains): CopyrightID 0x16943d91f3f414c0f6c361743d9fc37115ed5b73404bbd1da522d28eb4baa156. Chain 2 (Bitcoin): anchored in block 953657 (2026-06-14T16:43:25Z). Bridge: the canonical record inside this Bitcoin proof contains the same CopyrightID. Verify: download https://artists.proofprofile.net/proofs/artist/4d43a1f9-cf6c-4738-9944-fbc778aa2835.json and https://artists.proofprofile.net/proofs/artist/4d43a1f9-cf6c-4738-9944-fbc778aa2835.ots, run `ots verify -f record.json proof.ots` (https://opentimestamps.org).
Busoni: Violin Concerto, Op. 35a & Violin Sonata No. 2, Op. 36a
Brahms: Violin Sonatas No. 1, Op. 78 & No. 3, Op. 108
Beethoven: Violin Sonatas No. 5, Op. 24 "Spring" & No. 6, Op. 30/1
Mozart: Trio in E-Flat Major, K.498 - Beethoven: Trio No. 7 in B-Flat Major, Op. 11
Mozart: Trio pour piano, clarinette et alto, K. 498 - Beethoven: Trio pour piano, clarinette et violoncelle, Op. 11 (Mono Version)