Violin typically are lower in pitch than the G-string; these strings are usually tuned to C, F, and B. If the instrument's playing length, or string length from nut to bridge, is equal to that of an ordinary full-scale violin; i.e., a bit less than , then it may be properly termed a violin. Some such instruments are somewhat longer and should be regarded as violas. Violins with five strings or more are typically used in jazz or folk music. Some custom-made instruments have extra strings which are not bowed, but which sound sympathetically, due to the vibrations of the bowed
Violin technique intervals of perfect fifths by bowing them in pairs. This puts the open strings in just intonation, which means the lower strings may sound flat compared to their nominal equal-tempered equivalents. In practice, this means some compromises must be made, and the strings not always tuned in perfect fifths, particularly on the viola and cello, where the lowest string is the C, three fifths away from the reference A, making the difference more apparent. Small, temporary tuning adjustments can also be made by stretching a string with the hand. A string may be flattened by pulling it above the fingerboard,