The middle of the string is pacified whilst the two halves vibrate a clear bell like tone. Also allows hand to turn tuning machine whilst note is sounding. Natural harmonics can usually be found at frets with position markers. Jet Harris, formerly with the Shadows instrumental group, used alternative tuning on a six string guitar to record the hit single Diamonds. All strings were tuned one tone down.
Many groups use alternative tuning.
This facilitates easier string bending as less tension is required to tune a lower note. The tone or voice of the instrument alters and may become distinctive. Listen for pulsing sound as you tune two notes together. Pulsing is caused by the sum and difference of the two notes you are comparing as you tune. The pulsing gets slower as you approach closer to being in tune and eventually stops when optimum tuning is achieved.