Iambic
Iambic verse metre, short-long.
What it means
Iambic (German jambisch) designates a verse metre of two syllables in which the light precedes the heavy: short-long, unstressed-stressed. The counterpart is the trochee with the reverse order. The terms come from ancient verse theory and are used in music in a transferred sense to describe basic rhythmic shapes.
Musical use
Musically, the iamb corresponds to the upbeat: a light note leads to a heavy one that lies on the beat. This shape marks a large part of Western music, because it has a goal — the motion strives forward toward the stressed note. Accordingly, trochaic formations, which begin on the stress and die away, act rather falling and concluded.
In the vocal texture, agreement of word stress and note stress is a basic rule of good writing: an iambic line of text calls for a setting with an upbeat, and a displacement against it stands out at once. In instrumental music the principle remains effective even without text, because phrases likewise have rises and falls.
Bear in mind that the musical transfer is not seamless: in verse theory it is about syllable length or stress, in music duration, position in the bar, volume, and harmonic tension are added, which can reinforce or contradict one another. Precisely from this arises part of the rhythmic appeal, for instance in syncopation.
In music the iambic rhythm corresponds to an upbeat with a following strong beat, for instance an eighth note and a quarter note. It belongs to the basic patterns of declamation and shapes many German songs, because the German language often begins with an unstressed syllable. In medieval modal notation it corresponds to the second rhythmic mode.
Performance practice
Treat the upbeat as what it is: leading toward, not beginning. Take it lighter than the goal note and let it urge instead of emphasizing it — the most common mistake is an upbeat that is too heavy, which cuts the phrase up. With vocal music, check the word stress and orient the articulation on it. And breathe before the upbeat, not between it and its goal.