Twenty Minutes - 18/09/2009

From the foyer stage at St David's Hall, Cardiff, Petroc Trelawny discusses the art of 'period performance' on modern instruments. Plus news from the United States on ground-breaking research on the musicians who first performed Haydn's masses, a report from Eisenstadt on the work known originally as the Mass for Troubled Times, and how Lord Nelson made his mark on musical history.