  
2
Stem
direction
If the notehead is above the middle line, the stem goes down; if
the notehead is below the middle line, the stem goes up; and if
the notehead is on the middle line, the stem can go either way.
(With all things equal, the stem will generally go down, though).

Often notes are connected with beams, though, with
one or more notes being both above, below, and/or on the middle
line. In such a case, the note that is farthest from the middle
line dictates the direction of all the stems of the notes to be
connected. Following are various examples demonstrating this.
Example 1
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The top note (fourth space, counting from the bottom of the
staff) is farther from the middle line than is the lower note
and will dictate the direction of both stems--down.
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Example 2
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The second line note is the farthest from the middle line
than any of the other three notes. Because its notehead
is below the middle line, all stems will go up.
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Example 3
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These two notes are equal distant from the middle line. The
stems could go either direction, but usually go down unless
some other factor is involved. For example, if all the
other stems of notes in the same measure were going up, these
would go up also.
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Example 4
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Notice that this example is similar to the third because
there is no single note that is farthest away from the middle
line. Here, though, the third note is below the middle
line and creates a lack of balance. Even though the
farthest notes are equal distant, the stems go up in this
example because there is a greater number of notes below the
middle line.
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Example 5
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This last example demonstrates that the first
rule of thumb is to find the note that is farthest from the
middle line. In this case, it is the first note (fifth
line). Even though the majority of noteheads are below
the middle line, the first note dictates the stem direction
of all the notes because it is the farthest from the middle
line. |
  
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