This is a piano piece ‘sang by a pianist’. It doesn’t mean that this is a work which shall be played in cantabile. In the end of this piece, there is an actual singing performance.
4 inventions were published first, and later doubles, one kind of variation, were added to the piece later.
The first piece freely treats two kinds of total serialism; they are tone lines which connects different 12 tones by 11 intervals and all intervals, from minor 2 to major 7. The second piece was written by the same technique used by O. Messiaen. Regarding the third piece, you can say if invention is the classical school, double is like the dance music in the baroque era. It is the forth piece that makes the whole work original. The main theme adopted here is folk songs in Kashima (Ibaraki prefecture), called “Hamakaki-uta (Katta-maki)”. Musical scale from the folk song is quoted in the piece. Performer of the piece is going to sing folk songs in this double. According to “Nihon Minyō Taikan (The general Survey of the Japanese Folksongs), a volume of Kantō region”, these folk songs are based on the music for netting for fishing and celebrating a big catch. The lyrics of the folk songs, sung in the piece of Shibata, is this:
(in roman letters) Hā gentaka gentaka gentaka yotto, Ara, yoitokonanona, Katta maku niha Denju ha iranai, Yoitokonanona, Kotosha hōnen hyakusyō ha nikoniko oebisu-gao dayo, Yoitokonanona.
“4 Inventions and 4 Doubles” was published in 1991. This is a work in Shibata’s last years.