Ulvi Cemal Erkin was a composer who was influenced by the Impressionist movement. This effect is particularly evident in timbre, texture, and chord elements. He composed works that combined traditional Turkish makam music with Western musical elements. He combined folk dances, Anatolian melodies, and usûls and/or scale of the Turkish makam music, and utilized pentatonic scales, whole-tone scale, and synthetic scales while creating melodies. Besides, synthetic scale structures, which Erkin utilized, are not limited to the Turkish makam music. However, while analysing the scale structures employed by Erkin, researchers focused on their similarities with Turkish makam music. Therefore, the structures of synthetic scales that differ from the Turkish makam music scales utilized by Erkin will be analysed in this study. The scope of the study is limited to Erkin’s Piano Sonata, 1st and 2nd Symphonies. Document analysis, literature review method and style analysis method will be employed in this study. As a result, Erkin utilized such synthetic scales as overtone, Neapolitan Major 6th, Asian Bartók, Hungarian Minor/Major. Beside, he employed ‘rotation’ structures of some Turkish makam music scale. In this way, he expanded range of scale he employed. A comparative analysis of his works with those of other composers would contribute to the field.