Zoltán Kodály became seriously interested in Transylvanian folk music when he had learnt about the results of Béla Bartók's collecting fieldworks in Székelyföld. The wealth of old-style tunes and classical ballads, and – above all – the recognition of the importance of pentatony inspired Kodály to take part personally in the exploration of Székely folk music. Székely musical folklore obviously intrigued him both as an ethnographer and as a composer. He collected nearly 600 tunes in 15 Székely localities in the Gyergyó Basin, the valley of the Kászon stream, and Bukovina. He arranged 66 of these melodies within such compositions as e.g. the Dances of Marosszék, the musical play The Spinning Room, Hungarian Folk Music (57 ballads and folk songs for voice and piano), Székely Lament for mixed voices, Bicinia Hungarica, Kádár Kata and Molnár Anna (both with chamber orchestra accompaniment), and Pentatonic Music. Apart from his own collection, he also used those of some of his contemporaries. The paper discusses the specificities of Kodály's techniques of arrangement. His inspiring advice for younger folklorists had an essential role in triggering the in-depth investigation of Central Transylvanian folk music.