In music, solfège (UK: /ˈsɒlfɛʒ/, US: /sɒlˈfɛʒ/; French: [sɔlfɛʒ]) or solfeggio (/sɒlˈfɛdʒioʊ/; Italian: [solˈfeddʒo]), also called sol-fa, solfa, solfeo, among many names, is a music education method used to teach aural skills, pitch and sight-reading of Western music. Solfège is a form of solmization, though the two terms are sometimes used interchangeably.
Syllables are assigned to the notes of the scale and enable the musician to audiate, or mentally hear, the pitches of a piece of music being seen for the first time and then to sing them aloud. Through the Renaissance (and much later in some shapenote publications) various interlocking 4, 5 and 6-note systems were employed to cover the octave. The tonic sol-fa method popularized the seven syllables commonly used in English-speaking countries: do (or doh in tonic sol-fa), re, mi, fa, so(l), la, and ti (or si), see below.
There are two current ways of applying solfège: 1) fixed do, where the syllables are always tied to specific pitches (e.g. “do” is always “C-natural”) and 2) movable do, where the syllables are assigned to scale degrees, with “do” always the first degree of the major scale.