Played with open fingering; Common tonic: C major, but also encountered in B♭ major, G major, &c.

1 hole for the upper thumb and 7 fingerholes (tonic C: b³-c4), plus a hole for the thumb of the lower hand, producing, when opened, d♯³ (e♭³); Some instruments have a double bored hole for the little finger of the lower hand (i.e. oo, as in recorders with a "baroque bore"), enabling to play b♭³/b³; Plus 2-3 ventholes in the bell (2 lateral, a 3rd at the back).
NB: Example(s) to be replaced with staff-notation.