opposite of remove-tag urgently needed!

[Werner LEMBERG]

Consider the following: A common voice, \top, has been defined which
holds all `global' items of a score: the rehearsal marks, the tempo
indications, etc.  This \top voice has to be included both in the full
score and in each part, e.g.

  score:

     << \top
        \flute
        \oboe
        ...
     >>

  flute:

     << \top
        \flute
     >>

  oboe:

     << \top
        \oboe
     >>

  ...

Let's assume the following code to produce an `Allegro' in \top:

  s1^"Vivo"

Within the full score, this item has to be moved down a bit:

  \once \override TextScript #'extra-offset = #'(0 . -1)
  s1^"Vivo"

The flute part needs this:

  \once \override TextScript #'extra-offset = #'(0 . 1)
  s1^"Vivo"

The oboe part this:

  \once \override TextScript #'extra-offset = #'(0 . 2)
  s1^"Vivo"

Putting everything together, the code in \top should look like this:

  \tag #'score \once \override TextScript #'extra-offset = #'(0 . -1)
  \tag #'flute \once \override TextScript #'extra-offset = #'(0 . 1)
  \tag #'oboe  \once \override TextScript #'extra-offset = #'(0 . 2)
  s1^"Vivo"

What I now want to do is this:

  score:

     \applymusic #(use-tag 'score)
       << \top
          \flute
          \oboe
          ...
       >>

  flute:

     \applymusic #(use-tag 'flute)
       << \top
          \flute
       >>

  oboe:

     \applymusic #(use-tag 'oboe)
       << \top
          \oboe
       >>

  ...

My Scheme knowledge is virtually non-existent.  Is there a good soul
who could contribute `use-tag'?  Or is there already a possibility
within lilypond to do what I want, and I've missed it?


    Werner