For example, in the guitar (like other stringed instruments but unlike the piano), open-string notes are not fretted and so require less hand-motion. Thus chords that contain open notes are more easily played and hence more frequently played in popular music, such as folk music. Many of the most popular tunings—standard tuning, open tunings, and new standard tuning—are rich in the open notes used by popular chords. Open tunings allow major triads to be played by barring one fret with only one finger, using the finger like a capo. On guitars without a zeroth fret (after the nut), the intonation of an open note may differ from then note when fretted on other strings; consequently, on some guitars, the sound of an open note may be inferior to that of a fretted note.
Stacking the C-major scale with thirds creates a chord progression Play (help·info), traditionally enumerated with the Roman numerals I, ii, iii, IV, V, vi, viio. Its major-key sub-progression C-F-G (I-IV-V) is conventional in popular music. In this progression, the minor triads ii-iii-vi appear in the relative minor key (Am)'s corresponding chord progression.