Sentence:  Badura-Skoda-Vienna Konzerthaus ( Westminster ) and Demus-Schubert Quartet ( Deutsche Grammophon ) <WSD>are</WSD> both warm toned , pleasantly lyrical , but rather slack and tensionless . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)