John Nottle:

>Could somebody answer a quite trivial but vexing question, please.  Does
>the stem of the note B natural, treble clef, middle line, go up or down?
>Is there a rule determining such?

I've been given at least two rules (maybe more, but I've forgotten them).

Rule 1: The stem goes up if the majority of the notes in the measure go
up.  Down if most of the notes in the measure go down.  However, if the
number of notes going up equal the number of notes going down (other than
the b), the rule is silent.

Rule 2: The stem goes up if the surrounding note-stems go up, down
otherwise.  The stem goes up if the following note-stems go up, down
otherwise.  The stem of the b goes in the same direction as the other
notes grouped with it.

Rule 3 (practical experience): The stem goes up if it would run into other
markings below.  The stem goes down if it would run into other markings
above.  The idea is legibility.

But I'm just a duffer.  Let's hear from real composers.

Steve Schwartz