A pacifist, Lynch returned to Ireland following the outbreak of World War II, where he became the country's premier concert pianist. During this phase of his career he premiered a number of works by leading Irish composers, including Brian Boydell's "Sonata for Cello and Piano" (1945) and Sean Ó Riada's "Nomos No. 4" (1959). Lynch also performed in the world première of English composer Ernest John Moeran's "Cello Sonata in A minor", given in Dublin in May 1947. He was joined by the composer's wife, cellist Peers Coetmore.