Peruvian huayra-puhura
The British museum possesses a huayra-puhura consisting of fourteen reed pipes of a brownish colour, tied together in two rows by means of thread, so as to form a double set of seven reeds. Both sets are almost exactly of the same dimensions and are placed side by side. The shortest of these reeds measure three inches, and the longest six and a half. In one set they are open at the bottom, and in the other they are closed. Consequently, octaves are produced. The reader is probably aware that the closing of a pipe at the end raises its pitch an octave. Thus, in our organ, the so-called stopped diapason, a set of closed pipes, requires tubes of only half the length of those which constitute the open diapason, although both these stops produce tones in the same pitch; the only difference between them being the quality of sound, which in the former is less bright than in the latter.