Function offbeat_click_track 

pub fn offbeat_click_track(
    bpm: f32,
    secs: f32,
    offbeat: f32,
    format: AudioFormat,
) -> Vec<f32>

A click track at bpm carrying an extra click on every off-beat, at offbeat times the on-beat amplitude — the double-time trap (Plan 0095 Phase 1).

At offbeat = 0 this is click_track’s pattern; at offbeat = 1 it is literally a click train at twice bpm and there is no ground truth left to find. In between, the notated tempo is bpm while the onset envelope’s strongest short-lag periodicity sits at half the beat period, which is the arrangement that invites a tempo estimator to read the octave above.