For tuning harmonium to 22 Shrutis, we required a stable and accurate musical note for every Shruti as a reference standard, and we had to develope a method to play all the 22 Shrutis on the Synthesizer.
The "Synthesizer" is so called because it can "synthesize and play minute frequencies" within the range of the keyboard.
This is possible because, the distance between any 2 consecutive keys can be divided into 100 equal parts or 'Cents' and each one of them can be played and heard very easily. Such minute adjustments in the pitch of the note are possible to be done only electronically.
For eg., if key 'A' is at 440 Hz, the next key 'B flat' will be at 440 x 1.0594631 = 466.16 Hz. The difference between 466.16 and 440, is 26.16.
When this is divided into 100 parts or 'Cents', 1 Cent between these 2 keys will be of 0.2616 Hz.
The 1st Cent therefore will be at 440 + 0.2616 = 440.2616 Hz. The 2nd Cent will be at 440.2616 + 0.2616 = 440.5232, and so on. Like this, all '100 Cents' can be played between all keys from any Shadja to Upper Shadja.
The following table shows the 'Cents' (taking any key as the Shadja) on which the 22 Shrutis can be accurately played. (Refer to following table)