Extension
Lengthening phrase structure.
What it means
Extension designates the lengthening of a phrase beyond its expected measure. The basic unit of much music of the eighteenth and nineteenth centuries is the four-bar section, from which eight- and sixteen-bar periods are built. An extension breaks through this grid: by repetition of a member, by inserted sequences, by delay of the cadence, or by an appendix after the actual close. The result is a phrase of five, six, or more bars.
In the notation
An extension becomes recognizable only in comparison with expectation: one counts the bars of a phrase and notices that the ending comes later than assumed. Frequent signs are repeated motivic members, extended cadential sections with a closing chord deferred several times, or pedal points that hold tension.
Musical use
The procedure is an essential means of expression: where a phrase becomes longer, tension arises, because the ear expects the ending and does not get it. Composers use this at climaxes, before important cadences, and at the end of movements, where an ending is extended several times. Conversely there are also shortenings that surprise. Whoever recognizes such places understands why a piece of music pushes or pauses at certain points — it is due to the departure from the grid, not to the volume.
Performance practice
When working up a piece, count the groups of bars and mark where a phrase turns out longer than expected; shape these places deliberately instead of glossing over them. Hold the tension during the delay, for instance through a constant or slightly growing tempo, and release it only with the cadence. Avoid emphasizing every four-bar section equally, because otherwise the departure does not stand out. In an ensemble, agree how extended cadences are handled in time.
Note that extensions often stand near climaxes and produce the tension there: whoever overlooks them plays the passage flat. Mark such bars and decide how you shape the delay — usually a constant or slightly growing tempo carries more than holding back. Watch for pedal points, which often serve as a means of lengthening.