This is what I remember to have read about the topic of 22 shrutis and microtones which Bharatamuni had discovered in ancient times by playing on two veenas side by side and comparing the tones of the one with the other.
With the resurgence of the pursuit of academic understanding of the theory underlying the traditional Indian music, and the efforts of stalwarts like Vishnu Digambar Paluskar (founder of the Gandharva Mahavidyalaya of Lahore) and Vishnu Narayan Bhatkhande (founder of the Bhatkhande Music Institute of Lucknow), some like E. Clements, an ICS officer and enthusiast of Indian Classical Music, KB Deval (brother of the famous Marathi dramatist GB Deval) and a few oythers had built a harmonium that was capable of playing the 22 shrutis. They made efforts to popularize it through Musical Conferences and to make a commercial product from it. But it could not catch up with professional players of harmonium or musicologists like Bhatkhande.and died out in the course of time.
At present Dr Vidyadhar Oke, a medical practitioner and a noted accompanyist in concerts, uses such an instrument. For more, see his website
http://www.22shruti.com/
Arvind Kolhatkar.