[...]
Without getting too technical, objects are things that you can
create, have
properties and relationships with other well-defined objects.
This is true for things like staves, staff groups, scores, books,
etc.
You can say: \new Staff = { ... } to create a new staff because
there is
an object class called Staff that is well-defined.
It has known properties like Staff.TimeSignature, Staff.extraNatural,
etc.
Other objects (Staff Groups, Books, etc.) know how to handle this
Staff
object, or several Staff objects.
However, in the case of "instrument", there is no such object so you
cannot
create one.
There are certainly properties of other objects (namely, staves) that
have
"instrument" in the name, like Staff.instrumentName,
Staff.shortInstrumentName, Staff,midiInstrument.
However, these are *properties of a Staff object*.
There is no way to create an "instrument" outside the context of a
staff,
or identify or change its properties.
You cannot add an instrument to a staff or any other object.
If there were, the syntax might be more like:
violin = \new Instrument {
Instrument.name = 'violin'
Instrument.shortName = 'v.'
Instrument.midi = 'violin'
Instrument.clef = treble
...
}
\new Staff {
Staff.Instrument = \violin
\violinMusic
}
As an aside, an outstanding problem with lilypond is that it is
difficult
to write multi-instrument parts.
This points to a lack of clarity of design around the distinction
between a
voice, instrument and staff.
At its core is the lack of a coherent concept of instrument.
Which is to say, while you might point to the Staff as the place
where most
instrument information is situated, Staff and Instrument are clearly
not
identical concepts, nor is Instrument a proper subset of a Staff.
Perhaps the reason there is no such Instrument object in lilypond is
that
an "instrument" is not a grob.
There is no place that an "instrument" appears on the page, except as
a
label for a staff.
Yet, for the purpose of this discussion, it is clear that everyone
thinks
in terms of "instruments".
So, the documentation ought to explain exactly how this commonsense
conceptual notion of "instrument" maps to the actual objects and
properties
that are available.