Note stem
Vertical stroke on a notehead.
What it means
The note stem is the vertical stroke on the notehead. It belongs to all note values from the half note downward; the whole note has none. By itself it only says that the note is shorter than a whole note — only together with the filling of the head and any flags does the exact value result. At the same time it is the carrier of all flags and beams and thus the joint on which the rhythmic information hangs.
In the notation
The stem attaches to the right of the head when it leads upward, and to the left when it leads downward. In monophonic writing its direction follows the position: below the middle line it points upward, above it downward; on the middle line the surroundings decide. In polyphonic systems a different order holds, one more important than position — the upper voice consistently gets stems up, the lower voice stems down, so that the eye can tell the voices apart. If both voices have the same note, one head carries two stems in opposite directions. The usual length is about an octave; with beamed groups it is adjusted.
Musical use
For reading polyphonic settings, stem direction is the most reliable information about voice membership — more reliable than the spatial proximity of noteheads, which is misleading at voice crossings. In choral scores, where two voices share one staff, and in polyphonic piano writing, it is therefore indispensable. The stem is to be distinguished from Stiel, which means the same thing and is merely another word for it.
Other names
Stiel is an older and regional designation for the note stem. It has the same meaning but is less usual in today's music engraving.
Performance practice
In polyphonic settings, watch the stem direction first and only afterward the position of the heads, when deciding what belongs together. With piano writing containing held middle voices, it is worthwhile to practise the voices separately by stem direction, so that each becomes clear on its own. When writing yourself, keep attachment point and direction consistent — a wrongly placed stem makes it unclear, with closely spaced notes, which head is meant.