For the feeltone line of portable monochords (the Monolini or the Monolina) we offer five flavors C, A, G, F, D with C being the highest note and D the lowest.
All Monolinas have 34 strings: 24 overtone strings, 5 bass strings (one octave lower than the overtone) and 5 strings tuned to the interval of a fifth from the tonic string. Included are also 5 bridges for the overtone strings and a template that allows you to have accent melody notes tuned to either a major or minor pentatonic (5-note) scale. (You can also tune the melody notes to alternate scales of your choosing.)
The feeltone Company (based in Northern Germany) is working with a string maker that designs and creates strings that create the most volume and brilliance for each note, based on each tuning. The strings vary in material and design from the thin steel strings to the thicker "braided" bass strings (with copper coiling around an inner string), to create the right sound. The higher the note, the thinner the string. A thin string produces more overtones but less bass and physical sensation.
Your first choice should be the sound "flavor" that resonates best with you and we have created a set of videos below that allow you to listen to the different tunings. Another consideration, if you're playing in a group of people (where multiple instruments will be played together at the same time), is the key the other instruments are in.
Each Monolina can be tuned in 440 Hz, 432 Hz, (or any other reference tuning).
While you can tune the strings up or down a couple of 1/2-steps, if the strings are relaxed too much they won't have the correct vibration and brilliance, and if they get too tight, they might snap.