harmonicNote

[Dan Eble]

The NR has this:

> harmonicNote [music] - note (music)
> Print note with a diamond-shaped note head. 

Does \harmonicNote c4 do more than c4\harmonic?  If so, it would be nice to 
document what.  If not, perhaps convert-ly could replace it out of existence.

If a documentation update is undertaken, this related note seems to be untrue:

> Note: \harmonic must be placed inside a chord construct even if there is only 
> a single note.
— 
Dan