txtDefinition=In {\uldb quartet}{\v 154839} playing, the process of adjusting the four open (that is, unstopped) {\uldb strings}{\v 97871} to their exact {\uldb pitches}{\v 92779} a {\uldb perfect fifth}{\v 91593} apart (in practice this {\uldb interval}{\v 84848} is slightly smaller). Because of changes in temperature and humidity, as well as the general stress on the strings when played, string players must tune frequently\'97though hopefully no more than once a {\uldb movement}{\v 151907}! A {\uldb note}{\v 89586} or {\uldb chord}{\v 76801} is said to be \'93in tune\'94 or \'93out of tune.\'94
