Data for: Isochrony and rhythmic interaction in ape duetting

Animals and recordings Six habituated gibbon familiar groups were followed, with a total of 12 individuals and 215 songs, and specifically 157 female contributions to duet, 157 male contributions to duet and 58 male solos. Four groups were inhabiting the forests of Huai Kha Khaeng Wildlife Sanctuary (Thailand), and two other ex-situ groups were living at the Cappeller faunistic park (Corvigliano, Italy) and the Falconara zoo park (Ancona, Italy). We recorded the animals between 6:00AM and 12:00AM using a Sennheiser ME67 microphone connected to a solid-state digital audio recorder Tascam DR-100MKII (44.1KHz sampling rate). All vocalizations were recorded at 5–50 meters distance from the animals, aiming the microphone toward the individual vocalizing to maximize recording quality. Acoustic analyses We edited the songs using Praat 6.0.14 and saved them as WAV audio files. Field notes and video recordings allowed us to recognize and separate individual contributions to each song; each annotated contribution was subsequently saved as a single Praat TextGrid, an object featuring onset and offset of each note. A computing cluster (OCCAM) processed all 196768 vocal units via a custom Praat script and exported all onsets of song units from separate TextGrids into one .csv datasheet. We calculated the temporal interval between an onset and the next one, which defines an inter-onset interval (tk). We focused on all tk ≤5 sec, as this value is typically hypothesized as the upper limit for meter perception and performance in humans, and there is no quantitative evidence about an upper threshold on other apes. We calculated the tempo frequency as the inverse of peak values of tk per song type (Hz). The ratio (rk) was then calculated between a tk and the next one, tk+1, as tk/(tk+tk+1).