I have often 'ghosted' through pieces prior to an audible run through. This involves holding the flute, clarinet, saxophone (or whatever) and just moving the fingers. It saves tiring the lip unnecessarily as well as the ears of anyone in range. In a group situation it also prevents the sonic chaos that ensues when everyone is trying to practise their part at the same time.
As a reed and pipe player this method has a few shortcomings, one being the accurate pitching of the note, especially on the flute where a controlled overblowing is required to determine the register in which one is playing along with subtle changes in the embouchure to adjust the timbre and tuning.
Imagine my delight when a student arrived the other day and told me he had discovered air clarinet and this enabled him to practise at night without disturbing the neighbours. I assumed he meant either what I call ghosting or else imagining holding the instrument and moving the fingers as required. The latter, especially when applied to scales or other patterns of notes, I find a sure fire cure for insomnia.
What my student meant, in fact, was the removal of the reed and then playing as normal. He assured me he could hear the notes and that it gave him a sense of how much air would be required to play the piece. When I put this to the test I found that I could hear the notes fairly accurately in the chalumeau (bottom) register but that they were unsurprisingly absent above that. And while it may be satisfying on some level to blow into the instrument it is of little use in determining the breath control that will be required when playing 'for real'. Unlike saxophones and flutes, which have conical bores, the clarinet is a cylinder and it requires far less breath to make it speak. I do run short of breath on occasions but more often I find the problem is finding the time to expel unused air from the lungs where it has gone stale.
Still, 'air clarinet' gives the instrument the kind of cool cache it probably hasn't enjoyed since Artie Shaw was at his peak. It's definitely a term I will coin.