An aspect of bassoon technique not found on any other woodwind is called "flicking". It involves the left hand thumb momentarily pressing, or "flicking" the high A, C and D keys at the beginning of certain notes in the middle octave to achieve a clean slur from a lower note. This eliminates cracking, or brief multiphonics that happens without the use of this technique. The alternative method is "venting", which requires that the register key be used as part of the full fingering as opposed to being open momentarily at the start of the note. This is sometimes called the "European style"; venting raises the intonation of the notes slightly, and it can be advantageous when tuning to higher frequencies. Some bassoonists flick A and B when tongued, for clarity of articulation, but flicking (or venting) is practically ubiquitous for slurs.