Full of rapid scale like passages, sweeping arpeggios, syncopated rhythms and repeating patterns, Glass’s musical language seems custom built for the étude form. Maybe the biggest surprise is that he has taken until now to complete this set of 20 studies. In fact the first six or so date back to the mid-1990s, partly written in order to provide the composer with extra material for his solo piano tours but also as a pedagogical tool to develop his own technique. By the time Glass recorded the 10 Etudes that comprise Book 1, in 2003, he had already completed another six for Book 2.

The Etudes are therefore closely linked to Glass both as composer and performer; indeed, he has described them as self-portraits of sorts. However, there is little doubt that Maki Namekawa’s superlative performances on this recording transport these pieces to an entirely new plane. Etude 2, which may be familiar to some readers in its arrangement for two violins and string orchestra called Echorus (the Etude came first, in fact), is a case in point. Despite being uneven and at times alarmingly imprecise, Glass’s own recording shows plenty of weight and character, while Dennis Russell Davies’s performance from the 2008 Ruhr Piano Festival seems restrained and detached. Namekawa manages to balance both passion and precision, shaping the Etude’s oscillating patterns and resonant bass notes with sensitivity and control.

It’s an aspect of her playing which features throughout the set. Etude 6 is equally effective; Namekawa imbues its binary contrasts with dexterity, poise and power. During the 10th she sounds simultaneously motoric and melodic, and in the 11th uses the instrument’s full dynamic and colouristic potential. The Etudes of Book 2 are on the whole less virtuoso – Glass has described them as being ‘about the language of music itself’ – and there are times when the music lacks the subtlety and spontaneity of the opening set, becoming increasingly trapped by its harmonic sound world. However, the very final Etude, modelled on material taken from Glass’s music for Godfrey Reggio’s film Visitors, is a work of extraordinary power and beauty, at times quite unlike what one might expect from the composer. And with Namekawa at the piano, the set is worth buying for that Etude alone.