Rhythm
Rhythmic patterns which exist in the given material should be reused elsewhere in the piece, to give a feeling of cohesion. Don’t introduce rhythms which have a completely different style – for example, if the piece contains no syncopation, don’t add any!
Think about the momentum of the piece. Often, the rhythm of a piece will keep up a similar momentum throughout, but relax or slow down towards a cadence point. On the other hand, the rhythmic tension may well intensify towards a climax. Tension can be increased in rhythm by using faster or more complicated note values.
If the piece begins with an upbeat, consider whether it is appropriate to begin subsequent phrases also with an upbeat. Look for patterns to help you decide.
Generally, phrases should be well balanced. Look for questioning and answering phrases. An answering phrase will often contain very similar material (perhaps the same rhythm, for example), but will end with a different type of cadence, or perhaps with a modulation. Make sure that your phrases end smoothly enough, and not too abruptly.
In this Mendelssohn piece, the rhythm of bar 1 is repeated several times in the first eight bars. Each phrase ends with a cadence which is clearly visible by the use of minims (half notes). In the next eight bars, the rhythmic pattern is altered slightly (more quavers/eighth notes are used), but the link between bars 1-8 and 9-16 is very evident – both use a dotted rhythm on the first beat of the bar, and are built with even four-bar phrases.
