Fourth-based harmony became important in the work of Slavic and Scandinavian composers such as Modest Mussorgsky, Leoš Janáček, and Jean Sibelius. These composers used this harmony in a pungent, uncovered, almost archaic way, often incorporating the folk music of their particular homelands. Sibelius' "Piano Sonata in F-Major op. 12" of 1893 used tremolo passages of near-quartal harmony in a way that was relatively difficult and modern. Even in the example from Mussorgsky's piano-cycle "Pictures at an Exhibition" "(Избушка на курьих ножках (Баба-Яга) – The Hut on Fowl's Legs)" ([//upload.wikimedia.org/wikipedia/commons/2/29/Baba_Yaga_Quarten_for_wikipedia.mid Listen]) the fourth always makes an "unvarnished" entrance.