Musical Elements: Tempo, Metre and Rhythm

Tempo

Tempo denotes the speed at which a piece of music is played.
It is generally indicated at the beginning of a piece with an Italian word, such as Allegro (fast), Andante (walking pace), or Adagio (slow).
Composers may alter the tempo within a composition to create contrast or express different emotions. For example, a sudden change to a quicker tempo (Accelerando) can create tension, while a switch to a slower pace (Ritardando) can offer resolution.

Metre orients the rhythmic pulse in bars or measures, structured around the pattern of strong and weak beats.
Metres are characterised as duple (two beats per measure), triple (three beats per measure), quadruple (four beats per measure) etc.
More complex meters, such as compound meters that iterate a pattern of 6/8 or 9/8, or irregular meters (e.g., 5/4) are also employed in some compositions.
Music can also be ametric, lacking a clear, regular pulse.

Rhythm is dictated by the length and grouping of sounds and silences in music.
It involves elements such as beats, accents, syncopation (where a normally weak beat is emphasised), and cross-rhythm (the simultaneous use of conflicting rhythmic patterns).
Polyrhythm is a complex pattern employing two or more rhythms at once.
Rhythm in a piece can be quite regular (as in a march), or it can be free and flexible, as in much of 20th-century music.

Tempo, metre, and rhythm are all mutually influencing. Changes in one aspect can fundamentally transform the structure and feel of a piece.
A shift in tempo can change the overall energy of a composition and heavily impact its emotional resonance.
Playing with metre can create rhythmic surprises, a sense of instability, or new layers of emphasis and accent.
Rhythmic variation is another dimension of musical manipulation that can affect the mood, complexity and progression of a piece.
Understanding these three elements in relation to each other is crucial for both performing and analysing music.