TRANSITION is a word which has several different senses. It is most commonly used in a vague way as synonymous with modulation. Some writers, wishing to limit it more strictly, use it for the actual moment of passage from one key to another; and again it is sometimes used to distinguish those short subordinate flights out of one key into another, which are so often met with in modern music, from the more prominent and deliberate changes of key which form an important feature in the structure of a movement. The following example from Beethoven's Sonata in B♭, op. 106, is an illustration of the process defined by this latter meaning of the term; the transition being from F♯ minor to G major and back:—

{ << \new Staff \relative a' { \override Score.TimeSignature #'stencil = ##f \time 6/8 \key fis \minor
 << { <a fis>4 <gis eis>8 q4 <g e cis>8 |
      \appoggiatura g8 b'!4 a8 g4 fis8 | e4 fis8 g4 fis,8 | %eol1
      fis8 <a fis> <cis a fis> <cis gis eis>4 q8 |
      q4 <a fis>8 s_"etc." } \\
    { r8 <dis, bis> cis cis4 s8 | r8 b' a g4. | g4. g4 } >> }
\new Staff \relative c { \clef bass \key fis \minor
 <cis fis a>4 <cis eis gis>8 q4 <cis e g bes>8 |
 <d g b!>4. << { d'4 d8 | e4. d4 } \\ { <b g>4. c b4 } >> d8 | %eol1
 d[ cis] <cis a fis cis> <cis gis eis cis>4 q8 | q4 <cis a fis>8 s } >> }
[See Modulation.]