Fixed do

In fixed-do solfege the syllables are names for pitches, not for steps of the scale: do is C, re is D, mi is E, fa is F, sol is G, la is A and si (or ti) is B, in every key. A melody in G major therefore starts on sol, not on do, and a sharp or flat changes the pitch but not the syllable. Fixed do is the convention in France, Italy, Spain and parts of Latin America, where the syllables are the everyday names of the notes. Tonic solfa and jianpu use movable do instead, where do (1) is the first note of the key, so the same syllables describe the same steps in any key.

Etymology & origin

The syllables come from Guido of Arezzo's eleventh-century ut, re, mi, fa, sol, la. In the fixed-do countries they became the names of the notes themselves, with ut replaced by do and si added for the seventh.

In context

Example	What it means
G major in fixed do: sol la si do re mi fa# sol	The key's first note is sol, because G is always sol
G major in tonic solfa: d r m f s l t d	The same scale in movable do: doh is G, so the scale starts on doh
do = C in every key	The whole rule of fixed do in one line

Sources

Reference: en.wikipedia.org , consulted for the definition above; DomiSol's wording is original.