Wolfgang Amadeus Mozart (1756-1791) was an Austrian keyboardist, violinist and composer.  In his short life he wrote many symphonies, operas, concertos, vocal pieces, piano sonatas, violin sonatas, works for various small instrumental ensembles, as well as masses and other sacred music.  In this Adagio Mozart demonstrated emotional intensity and harmonic richness with a romantic style.
Please note: this clip is not the complete track -- it has been truncated to maintain a reasonable file size.