\version "2.19.35"

%%%%%%%%%% The relevant parts of my modified version of snippet 739 %%%%%%%%%%
% calculate x-alignment based on attribute text + dynamic text
% this has to be a markup-command to get stencil-extent based on (interpret-markup layout props ...)
#(define-markup-command (center-dynatr layout props atr-text dyn)(markup? string?)
   "x-align on center of dynamic"
   (let* (
           (text (string-append " " atr-text ))
           (atr-stencil (interpret-markup layout props (markup #:normal-text #:italic text)))
           (dyn-stencil (interpret-markup layout props (markup #:dynamic dyn)))
           (atr-x-ext (ly:stencil-extent atr-stencil X))
           (dyn-x-ext (ly:stencil-extent dyn-stencil X))
           (atr-x (- (cdr atr-x-ext)(car atr-x-ext)))
           (dyn-x (- (cdr dyn-x-ext)(car dyn-x-ext)))
           (x-align
            (* (-
                (/ (/ dyn-x 2) (+ atr-x dyn-x) )
                0.5) 2)
            )
           )
     (interpret-markup layout props (markup #:halign x-align #:concat (#:dynamic dyn #:normal-text #:italic text)))
     ))
% define a 'new' attributed dynamic script
#(define (make-dynamic-atr-script dyn atr)
   (let ((dynamic (make-dynamic-script (markup #:center-dynatr atr dyn))))
     (ly:music-set-property! dynamic 'tweaks (acons 'X-offset 0 (ly:music-property dynamic 'tweaks)))
     dynamic))

% define some attributed dynamics
mpdolce = #(make-dynamic-atr-script "mp" "dolce")
%%%%%%%%%% Modified version of snippet 739 (ends) %%%%%%%%%%

music = \new Voice {
  \relative {
    \clef bass
    \key es \major
    r2 r8 f8(\mpdolce e f) |
    %        \override DynamicLineSpanner.staff-padding = #2.5
    r2 r8 bes,8(\mpdolce a bes) |
  }
}

\score {
  \new StaffGroup
  \new Staff {
    \music
  }
}