When approached with a unity / variety question...
Composers aim to achieve an effective balance between unity and variety.
UNITY
UNITY is achieved in a piece of music by repetition of ideas.
Rhythm
ostinati; regular use of rhythmic motifs
Tempo
consistent speed maintained
Metre
consistent pulse and unchanging time signature
Melody
repeated melodic motifs
regular contour
stays in the same register
consistent use of steps or leaps
regular phrasing
Harmony
emphasis on particular interval
generally consonant or dissonant
use of pedal tone or drone
consistent use of chord type and sonority
regular rate of harmonic change
repetition of progression
regular use of cadences
Tonality
constant tonal centre
consistently atonal
return to opening key
Tone colour
same instrumental or vocal grouping maintained
same instrument associated with melody or bass or accompaniment
Expressive techniques
consistent dynamic level
established pattern of repeated dynamics
consistent approach to articulation or ornamentation
Texture
consistent pattern of melody and accompaniment, or if melody and counter melodies.
VARIETY
VARIETY is achieved in a piece of music by contrasting ideas.
Rhythm
change of note patterns
syncopation
variation of motifs
Tempo
accel. or ritard.
use of rubato
sudden change of speed
Meter
irregular time signature
additive meter
polymeter
Melody
variable contour or range
contrast of steps and leaps
development of motifs
irregular phrasing
Harmony
change between consonant and dissonant
variable chord types
contrast in harmonic rhythm
new progressions
Tonality
modulation
change from diatonic to atonal
Tone colour
contrast in instrumental or vocal groupings
melody dovetailed between different instruments
use of acoustic and electronic sound sources
extremes of registers used
Expressive techniques
cresc. and descres. sudden f or p (terraced)
accents and sf, fp
contrast between legato and staccato
different ornaments used
Texture
change from homophonic to polyphonic
contrast between density and clarity
changing number of layers of sound
Structure
contrasting sections, episodes