1.   When he picked up the guitar, slung it round his neck, and started to tune the strings, there was no more doubt.

2.   All he carried was his bagful of graphite racquets and the little metal tuning fork that keeps their strings tuned to the proper pitch for aces and accolades.

3.   For instance, most guitar players use an electronic tuner that allows them to tune each string perfectly, instead of relying on the ear.

4.   Strings are tuned at half-step differences.

5.   These electronic gadgets listen to the sound of a strummed string and then use a meter to indicate when the string is tuned perfectly.