It is a metronome.
There are tons of web/etc metronomes out there but for some reason it's very common to have a lower bound on bpm, like 40 or so.
One way I like to practice is with a click/beep every beat one which is hard for slower tempos with that lower bound.
metronome -bpm 15 lets me do that for a 60 bpm tempo.
go install github.com/danp/metronome@latestThis program uses oto/v2 which does not requrire cgo for macOS or Windows. See docs for what's necessary on other platforms.