Re: Proposed new available and recommended behavior of \relative

[Jim Long]

On Sat, Mar 09, 2013 at 11:40:14AM +0100, David Kastrup wrote:
> 
> Well, the new mnemonic would be "first pitch after \relative is
> absolute"

I'm not sure whether this is profound or profane, so please
excuse, but....

For just the case of \relative WITHOUT a reference pitch:

I.  Am I correct that the CURRENT definition of \relatve 
without a reference pitch is that the reference pitch 
defaults to the absolute pitch c'?  In other words, 
\relative { \music } = \relative c' { \music } in the current
stable version?

II. Is it also true that for any absolute pitch { X } that
\relative f { X } is the same pitch?

So if somehow I've made two consecutive correct postulates,
wouldn't a user who used the mnemonic:

"If no reference pitch is given, then the first pitch after
\relative is relative to f"

be equally correct at predicting the output of the newly proposed
\relative?

I realize that this isn't an accurate description of the 
internals of the proposed change, but it seems that it
would produce the same effect.

"\relative f" was mentioned in discussion a few days ago, so
maybe I'm just slow on the uptake, but it seems that a devil's
advocate could say that the proposed change just changes the
default reference pitch from c' to f.

Under the proposed change, would not:

\relative { c d e f g a b c }
\relative { c' d e f g a b c }

be the same as

\relative f { c d e f g a b c }
\relative f { c' d e f g a b c }

I realize that may not be the way one would want the
documentation to read, but it works as a mnemonic.

So, addressing those who are put off by a perceived mixing of
absolute and relative music inside \relative {}, does this
mnemonic assuage your concerns:

"If \relative { ... } is specified without a reference pitch,
the reference pitch defaults to f."

All music inside \relative {} is still purely relative: relative
to either an explicit reference pitch, IF one is given; or
relative to f, if no reference pitch is given.

If Lilypond's internals choose to implement that by analysing
the first pitch as absolute, well, tomato, tomahto.  Absolute
pitches by definition are relative to f.

As for which is clearest to the user, document both mnemonics,
and let the user decide which way they prefer to think of it.
The behaviour is the same either way, yes?