This set of variations takes as its theme the children's song “Tsuki” (also known as “Tuki” or “Otsukisama”), which begins with the lyrics “Deta deta tsuki ga” (The moon has appeared, has appeared). “Tsuki” first appeared in Jinjo Shogaku Tokuhon Shoka (Songs for Elementary School Readers) published in 1910 (Meiji 43). This song collection was the first elementary school textbook compiled by the Ministry of Education, and its included works continued to be featured in subsequent song collections edited by the Ministry of Education, such as Jinjo Shogaku Shoka (Elementary School Songs, published 1911–1914). Songs like “Haru ga Kita” (Spring Has Come) and “Fuji no Yama” (Mount Fuji) are still widely beloved today. Jinjo Shogaku Tokuhon Shoka drew its lyrics from Jinjo Shogaku Tokuhon (Elementary School Readers), the Japanese language textbook of the time. Until then, Japanese shoka (school songs) largely relied on foreign songs, being created either by translating lyrics into Japanese or by using Western melodies as they were and adding new Japanese lyrics (a method known as sakka or tenshi). In contrast, this song collection is characterized by the fact that all its pieces were composed by Japanese hands.

Although the composer of “Tsuki” is unknown, Kiyoshi Nobutoki, the composer of this set of variations, stated, “I believe the melody was probably composed by Mr. Akataro Shimazaki.” He also hinted at its suitability as a theme for variations, saying of the piece that “that melody, overflowing with childlike innocence, can be delightfully varied.” According to Nobutoki’s recollections, Variations on the Children's Song “Tsuki” was composed around 1910, but the liner notes for the CD SP On-gen Fukkoku-ban Nobutoki Kiyoshi Sakuhin Shusei (SP Sound Source Restoration Edition: Collected Works of Kiyoshi Nobutoki) suggest it is highly likely to be a work from around 1920–22 (Taisho 9–11). Furthermore, the score for Variations on the Elementary School Song “Tsuki”, an orchestral arrangement of Nobutoki's work by Kuro Mashiko, also remains.

Nobutoki composed numerous suites, song cycles, and variations. In particular, this work, woven around a simple and unpretentious theme, fully brings out the charm of variations. The way the C major theme unfolds in various ways, changing key, meter, and rhythm, is reminiscent of the moon sometimes becoming shadowed and then shining brightly in the night sky.

Principal References

• Nobutoki Kiyoshi Piano Kyokushu (Collected Piano Works of Kiyoshi Nobutoki) (Tokyo: Shunjusha, 1958).
• SP On-gen Fukkoku-ban Nobutoki Kiyoshi Sakuhin Shusei (SP Sound Source Restoration Edition: Collected Works of Kiyoshi Nobutoki) (Tokyo: Japan Traditional Cultures Foundation, Victor, 2008).