Alternate tunings
Alternative tunings are regularly being used in fingerstyle music. The simplest variant of the standard EADGBE tuning is drop D. This means that the low E string is tuned down to D.
The advantage of playing in a different tuning is that certain combinations of tones suddenly become very easy to play, whereas in standard tuning they might even be impossible.
Some guitar players play always in alternate tunings, such as Pierre Bensusan, Andy McKee and Michael Hedges.

Maybe you have ever noticed that Andy McKee or John Mayer regularly tune some strings above standard tuning.
If you would like to try this yourself, be aware of the fact that the tension in the strings and the neck of the guitar goes up too. It shouldn’t be a problem to tune up one or two strings for a song, but make sure that you tune it back after playing. This prevents warping of the neck and the top. Please note also that you might break a string. Also keep in mind that sometimes your string might break. The guitarists mentioned are using other kind of strings than you do probably, and sometimes the construction of the guitar is adjusted to the higher tension.

In the video you see Masaaki Kishibe playing his song ‘Hana’. His guitar is in open D tuning (DADF#AD).