Composed at the commission of Kaori Nakajima. It was premiered at her recital and dedicated to her.

It consists of three movements: A "Toccata," B "Adagio: Variations without a Theme," and C "Harmonization." All movements use the fourth piece from the composer's past work, From the Shadow of Songs (1985) for five players, as their material. This source piece used a poem from the Man'yōshū ("Nubatama no sono yo no ume o tawasurete orazu kinikeri omoishi mono o") as lyrics, interwoven with a quotation from the medieval Carmina "Veri Dulcis" (Sweet Spring). While "Veri Dulcis" was clearly audible in the original From the Shadow of Songs, it became a more subtle motif in this sonata. This is the origin of the title.

In Movement A, the initial figure, pressed silently and sustained with the sostenuto pedal, is an omission of the repeated notes from "Veri Dulcis." In the published score, the second note is marked as His, but it should be Ais. This movement is structured so that "Veri Dulcis" gradually emerges like a fragrance as a reverberation in the background. Movement B consists of four variations and a coda from the first half of the original piece. "Veri Dulcis" is extended as a chord from measure 65. Movement C is a simple chord progression, but the changes from perfect consonances to clusters create music reminiscent of cross-sections of the shakuhachi's pure and impure tones. The total duration is approximately 16 minutes. Since there are many errors in the published score, it is advisable to inquire if an errata sheet is not included.