[dredmorbius]

Birdsong also occurs at a far greater rate / tempo than human ears are used to distinguishing. To fully appreciate most birdsong it must be slowed considerably. This is similar to many rodent calls (also rapid and high pitched), and contrasts with, say, whalesong, which must be sped up not only to raise it to a (human-) audible pitch, but for the patterns to be sensible to us.

Some human musicians and composers have played with similar themes, increasing or decreasing tempos by huge amounts. Examples of slow pieces include As Slow As Possible by John Cage, with a performance begun in 2001 due to end in 2640, and Longplayer by Jem Finer, which lasts 1,000 years. Musician and YouTube Adam Neely has an episode addressing the fastest tempos discernable by humans. At the upper range, the inter-beat range simply merges into a new soundform, at about 15--20 Hz, the lower bound of human audio perception.