DvoÅ Ã k wrote many operas ( the best known of which is Rusalka ) ; chamber music ( including a number of string quartets , and quintets ) ; songs ; choral music ; and piano music . DvoÅ Ã k 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 ) ; songs ; choral music ; and piano music .