The British painter Ceri Richards (1903-1971), music and piano lover, attaches a great place to music and poetry in his art. After the Second World War, musical references become more and more important in his work. Seen as his major achievement, the Cathédrale Engloutie series (ca. 1957-1967), inspired by the eponymous Prelude by Debussy, shows a truly original style and reveals major inspiration sources from the score such as the atmospheric and mood instructions to the pianist and the very precise musical citations of the score. The comparative analysis proposed in this article puts together music and art showing how the musical structures can be found in the paintings which titles are extracted from the Debussy’s score. The links between Debussy’s musical field and Richards’s painting field are also evocated.