A, B, Both pressure (A) and flow (B) at the onset of sound production do not differ significantly across experimental preparations. C, Two-tailed paired t tests show that the HNR is significantly decreased in the excised preparation (P4) compared with in situ (P1, *p < 0.05) and to the 24 – 48 h denervated syrinx (P3, **p < 0.01), which means that the amount of spectrum complexity increases significantly in the excised syrinx. N = 6, except for P4, where N = 4. Preparation P1, in situ phonation; preparation P2, in situ phonation after lesion of the bilateral tracheosyringeal branches of the hypoglossal nerve; preparation P3, in situ phonation 24 – 48 h after lesion; and preparation P4, excised in vitro preparation.