Sentence:  Miss Xydis ' earlier selections were Mendelssohn 's Variations Serieuses , in which each variation was nicely set off from the others ; Haydn 's Sonata in E minor , which <WSD>was</WSD> unfailingly pleasant in sound , and Chopin 's Sonata in B flat minor . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)