sentences:  Many of his works show the influence of Czech folk music, both in terms of elements such as rhythms and melodic shapes; amongst these are the two sets of Slavonic Dances, the "Symphonic Variations", and the overwhelming majority of his songs, but echoes of such influence are also found in his major choral works.Dvořák also wrote operas (of which the best known is "Rusalka"); serenades for string orchestra and wind ensemble; chamber music (including a number of string quartets and quintets); and piano music.While a large number of Dvořák's works were given opus numbers, these did not always bear a logical relationship to the order in which they were either written or published.