Sentence:  This <WSD>was</WSD> not an overriding drawback to enjoyment of the performances , however , except in the case of the opening work , Mozart 's Sonata in A ( K. 526 ) , which clattered along noisily in an unrelieved fashion . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)