An idioglot can be a musical instrument that plays only one note. This sort of idioglot is held in the mouth and plucked.
The vital feature that makes an instrument an idioglot is that the vibrating bit is an integral part of the instrument. It's not something like a clarinet, for example, where the vibrating reed has to be tied onto the mouthpiece.
An idioglot sounds a simple thing - and it is, really - but you can make quite complex sounds by singing along as you play. This will sometimes provide three notes: you'll get the note of the idioglot; the note sung; and a sort of growl of anguish as the two clash.
The Indian form of idioglot is called a morsing:
and is usually played as apart of an ensemble, or as an accompaniment to singing. It generally plays in time with the other instruments as a sort of echo.
The Philippino kubing:
and Hmong are similar sorts of things. (The video above is very short, but well worth hearing.)