All-fifths tuning has been approximated by the so-called "New Standard Tuning" (NST) of King Crimson's Robert Fripp, which NST replaces all-fifths' high B4 with a high G4. To build chords, Fripp uses "perfect intervals in fourths, fifths and octaves", so avoiding minor thirds and especially major thirds, which are sharp in equal temperament tuning (in comparison to thirds in just intonation). It is a challenge to adapt conventional guitar-chords to new standard tuning, which is based on all-fifths tuning. Some closely voiced jazz chords become impractical in NST and all-fifths tuning.