Luftpause
A brief, unwritten pause for breath in a musical phrase, typically indicated by a small comma or apostrophe above the staff.
In Depth
Luftpause (German for "air pause") is a momentary silence — shorter than any notated rest — that allows a singer or wind player to breathe, or any musician to create a subtle articulation between phrases. Marked with a small comma, tick mark, or apostrophe above the staff, it does not affect the underlying tempo or meter; rather, the time is "stolen" from the preceding note, which is slightly shortened to accommodate the pause.
Though originally a practical breathing instruction, the Luftpause has become an expressive tool. In orchestral music, a Luftpause in all parts simultaneously creates a tiny gap that gives special emphasis to what follows — a collective "intake of breath" before an important moment. Gustav Mahler used Luftpausen extensively and with great precision, and conductors often add them at phrase boundaries even where not notated, as a means of shaping the music's breathing and articulation.
The Luftpause is sometimes called a "breath mark" in English, but its function extends beyond breathing — string players and pianists use them too, for purely musical reasons of phrasing and articulation.