In January 1979, Thad suddenly moved to Copenhagen, Denmark (to the great surprise of his New York bandmates), where several other U.S. jazz musicians had gone to live. There he became the leader of The Danish Radio Big Band, and married a Danish woman (Lis). Jones transformed the Danish Radio Big Band into one of the world's best. The result can be heard on a live-recording from the Montmartre in Copenhagen. In July 1979 Jones formed a new big band, Eclipse, with which he recorded a live album, Eclipse. Several Americans were on the album: pianist Horace Parlan, baritonist Sahib Shihab, trumpeter Tim Hagans and trombonist/vocalist Richard B. Boone, along with trombonists Bjarne Thanning and Ture Larsen, trumpeter Lars Togeby, altoists Ole Thøger and Michael Hove, tenor saxophonist Bent Jædig, and Jesper Lundgaard on bass. Jones further composed for the Danish Radio Big Band and taught jazz at the Royal Danish Conservatory in Copenhagen. He studied composition formally during this period, and also took up the valve trombone.