Johann(es) Simon Mayr (also spelled Majer, Mayer, Maier), also known in Italian as Giovanni Simone Mayr or Simone Mayr (14 June 1763 â 2 December 1845), was a German composer. His music reflects the transition from the Classical to the Romantic musical era. He was an early inspiration to Rossini and taught and advocated for Donizetti.