Re: Scheme question on strict substitution

[Mats Bengtsson]

In my understanding, the difference between \override and \tweak is
that with \override, you can only specify the "time" at which the setting
should be active, i.e. if you have several notes or whatever that appear
simultaneous within the same context, then you can not affect them 
individually,
just all of them together. With \tweak, on the other hand, you can 
control each
object separately, for example to modify one note head out of several in 
a chord
or modifying one articulation out of several on the same note.

   /Mats

Trevor Bača wrote:
> I guess I've never really had a good grasp on how \tweak works; can
> anybody explain why the example above doesn't work with \overrides but
> does work with \tweaks?
>
> Section 9.3.5 "Objects connected to the input" says "In some cases, it
> is possible to take a short-cut for tuning graphical objects. For
> objects that result directly from a piece of the input, you can use
> the \tweak function ...". But I've never really understood what this
> means. What does it mean for an objected to "be connected to the
> input"? Are all objects connected to input? Objects only come about
> from input, right?
>
> Instead, of understanding "connectedness to input" as being behind
> \tweak, I've instead mentally adopted the idea that \tweak is
> necessary (instead of \override) when you want to separately modify
> the attributes of two or more objects that instantiate at the *same
> musical moment*. 9.5.3 gives the example of \tweaking noteheads in a
> chord, and the noteheads in a chord certainly instantiate at the same
> musical moment. Likewise for the nested tuplets in the example here:
> the nested tuplets instantiate at the same musical moment, so that
> seems to trigger the need for \tweak instead of \override.
>
> Is the understanding I've worked out for myself correct, ie, that we
> use \tweak when we want to modify objects that instantiate at the same
> musical moment? And, if so, maybe the idea of "sameness of musical
> moment" can replace the idea of "connectedness to input" in 9.3.5.

--
=============================================
        Mats Bengtsson
        Signal Processing
        Signals, Sensors and Systems
        Royal Institute of Technology
        SE-100 44  STOCKHOLM
        Sweden
        Phone: (+46) 8 790 8463                         
       Fax:   (+46) 8 790 7260
        Email: address@hidden
        WWW: http://www.s3.kth.se/~mabe
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