Sibelius began planning his Sixth Symphony, op. 104, in 1918, before the Fifth reached its final, definitive version: the Sixth took virtually five years to complete, and was first performed in 1923. It immediately attracted attention, and critics began at once to explore its structure. Sibelius seems to have been genuinely surprised at some of the revelations of the analysts and is recorded as saying that though investigators might find several interesting things going on in the work, ‘most people forget that it is, above all, a poem’. Sibelius's warning – typical of most composers, who generally seem content to forget the scaffolding of a work once it is completed – has done nothing to prevent analysts from probing into the Symphony.