Is there a word for instruments that are limited to only one octave, as opposed to instruments that can play multiple octaves? I think this is a matter of classifying instruments with a certain narrow musical range, regardless of where that range is on the spectrum of pitches.
Less than 1 octave: Berimbau, simple 4-hole flutes, various drums and other instruments that have a very limited range.
More than 1 octave: Piano, guitar, human whistling or singing.
I found polyphony & monophony but that is about more than one note at once, not multiple octaves - for example, I can whistle in many octaves but can only whistle one note at a time.