The piano trios of the Classical era, notably those of Haydn, are dominated by the piano part. The violin plays the melody only a certain amount of the time, and when it does, is often doubled by the piano. The cello part is very much subordinated, usually just doubling the bass line in the piano. It is thought that this practice was quite intentional on Haydn's part and was related to the sonority of the instruments of Haydn's day: the piano was fairly weak and "tinkling" in tone, and benefited from the tonal strengthening of other instruments. Mozart's five late (K. 496 and later) trios are generally felt to mark the assured arrival of the form, attentive to balanced voices and three-part dialogue.