18–20, Schoenberg turned back and revived old techniques, very self-consciously returning to and transforming tradition by the concluding songs of Pierrot lunaire (1912), Op. 21, with, e.g., intricately interrelated canons in "Der Mondfleck", clear waltz rhythms in "Serenade", a barcarolle ("Heimfahrt"), triadic harmony throughout "O alter Duft". Pierrot was received by Webern as a direction for the composition of his own Opp.