Fig. 3. Sound and muscle activity during the ring dove coo. (A,B,E,F,I,J) Typical results of (A,E,I) sound oscillograms and (B,F,J) spectrograms of the stereotyped ring dove coo, which consists of two syllables (S1, S2), followed by an inspiratory note (arrow in B) of three individuals D#1–3. Syllable S2 starts with a trill (tr). The result of the fundamental frequency analysis is superimposed on the spectrogram. The colour of the trace indicates the RMS value of the corresponding bin (yellow–red; low–high). (D,C,G,H,K,L) Electromyographic recording of TL (C,G,K) and (D,H,L) ST. EMG signal: upward, rectified and integrated with time-constant of 1 ms; downward, rectified. The part of the coo in the rectangle of dove D#1 is shown enlarged in Fig. 4. The timescale is the same for all panels.