One of Europe’s most esteemed music institutions, the Sibelius Academy in Finland, has acquired an extremely rare instrument: a radically redesigned quarter-tone piano. With a mechanism almost identical to its regularly tuned cousin, the most conspicuous difference from a conventional piano is the keyboard: instead of dividing the octave into 12 pitches, it is divided into 24. Other quarter-tone piano designs have previously been built but have often been bulky and difficult to play.

Two former students of the Sibelius Academy, pianist Elisa Järvi and composer Sampo Haapamäki, have been collaborating for almost a decade to realise a more ergonomically designed full-size quarter-tone piano. Previous solutions to the quarter-tone piano involved two separate instruments, or multiple manuals, which created limitations on the complexity and virtuosity that could be reasonably expected by a composer. With assistance from the Sibelius Academy development centre, Järvi and Haapamäki first created a one-octave proof-of-concept, before a full-scale prototype of their design began construction in 2014.

The use of quarter-tones is fairly common among contemporary compositions, but the concept of breaking the scale down into smaller divisions is hundreds of years old. The equal division of the octave, known as well-tempered,...