His synaesthetic talent in combining natural impressions, colours and sounds allowed Sibelius to use a broad variety of keys in his first cyclic chamber music works. In 1889, he began to use ambiguous modal sound planes and modes other than major and minor, mostly to express a Finnish tone. Examples from the F major violin sonata, the piano quintet and the quartet op. 4 anticipate the rich palette of sound nuances in Sibelius's later works for orchestra. In the quartet Voces intimae Sibelius used modes in variable ways. Beside the traditional modes and whole-tone scale sections we also find an enormous variety of colours in the ingenious use of major and minor keys.