Re: simple scheme function #{ $note #}

[Aaron Hill]

On 2018-05-11 14:17, David Kastrup wrote:
> Aaron Hill <address@hidden> writes:
> > The error message reads pretty clearly, though.  The result of a music
> > function cannot be a single NOTENAME_PITCH.
>
> The result of a music function cannot be a pitch, period.  It has to be
> a music expression.  A pitch is not a music expression.

I think we are in violent agreement here.  It is going to be pointless 
to nitpick details that are likely irrelevant and off-topic.  So in an 
effort to circle back to summarize and address the original question...

A music function must evaluate to a music expression.

The reason why #{ $p #} does not work as the body of a music function is 
that it will only evaluate to a pitch not a note, and that pitch by 
itself is not enough to create a music expression.

#{ $p 4 #} works because a pitch followed by a duration clearly defines 
a note, which is enough to form a music expression.

#{ $p $p #} and #{ $p a' #}, even though missing explicit durations, 
both work because two or more bare pitches can be interpreted as a 
sequence of notes where the duration of the notes will be defined by 
preceding context.

Finally, #{ { $p } #} works because the inner braces specifically 
instantiate a music expression.  Though, again, the note resulting from 
the bare pitch will have to inherit its duration from prior notes or 
default values.

Clear as mud?  :)

-- Aaron Hill