Do you know the transverse flute family? The concert flute in C, the most played, the piccolo in C, one octave above, the alto flute in G,a fourth below the concert flute, and bass flute in C, one octave below the concert flute, with a curved head to allow the musician to reach the keys.
But there is more, the contrabass flute two octaves below the concert flute, folded in the shape of a four. Quite unknown instrument, it id played mostly in flute ensembles.
The subcontrabass flute, three octaves below the concert flute, is more than 4 meters (13 feet) long, only exists a few copies, made with metal or PVC.
Peter Sheridan is a bass flutes specialist, he’s at the origin of the deepest transverse flute, the hyperbass, more than 8 meters (26 feet) long, four octaves below the concert flute. Its lowest note, C 0, near 16Hz, passes the infrasound border.
I only found a quite bad video of this flute, I will update the article if I find out another one, if you see one send it to me! Bonus video, the biggest bansuri flute in the world, my fingers suffer just by watching..!