%%%%%%%%%%% functions %%%%%%%%%%%%%%%%%

#(define currentmoment (ly:make-moment 0 1 0 1))

#(define (clean-Music music)
(music-filter
	(lambda (evt)  ;% don't keep simultaneous and  sequential music with empty 'elements
		(or (not (eq? 'EventChord (ly:music-property evt 'name)))
			(pair? (ly:music-property evt 'elements))
			(pair? (ly:music-property evt 'articulations))
			(ly:music? (ly:music-property evt 'element))
		)
	)
	(music-filter ;% don't keep articulations or slurs with no notes assigned to
		(lambda (evt)
			(let ((elts (ly:music-property evt 'elements)))
			(not 
				(and 
					(eq? (ly:music-property evt 'name) 'EventChord)
					(pair? elts)
					(not (memq	(ly:music-property (car elts) 'name) 
								(list 'NoteEvent 'RestEvent)))
					)))
		)					 					
		music))	 	
)

#(define (extract-Music music from to) ;% from and to as moment
(let* (
	(musicname (ly:music-property music 'name))
	(elts (ly:music-property music 'elements))
	(elt  (ly:music-property music 'element))
	(dur (ly:music-property music 'duration))
	(res music)
	)
(begin
	;%(display musicname)(newline)
	(cond 
		((pair? elts)
			(if (not (eq? musicname 'SimultaneousMusic))
				(set! (ly:music-property music 'elements) ;% for SequentialMusic
					(filter 
						(lambda (evt)(extract-Music evt from to))
						elts
					)
				)											;% for SimultaneousMusic
				(let (	(maxmoment (ly:make-moment 0 1 0 1))
						(savemoment currentmoment)
						(tempmoment (ly:make-moment 0 1 0 1))
						(resmusic (make-music 'Music)))
				(begin		
					(set! (ly:music-property music 'elements)
							(filter 
								(lambda (evt)
									(begin
										(set! resmusic (extract-Music evt from to))
										(set! tempmoment (ly:moment-sub currentmoment savemoment))
										(if (ly:moment<? maxmoment tempmoment)
											(set! maxmoment tempmoment)) ;% keep the biggest length
										(set! currentmoment savemoment) ;%restore the previous length
										resmusic
									)
								)
								elts
							)
					)
					(set! currentmoment (ly:moment-add savemoment maxmoment))	
				))  	
			)	
		)
		((ly:music? elt)
				(extract-Music elt from to)
		)
		((ly:duration? dur)
			(begin
				;%(display dur)(newline)
				(set! currentmoment (ly:moment-add 
									currentmoment 
									(ly:duration-length dur)))
				;%(display currentmoment)(newline)
				(set! res 
					(and
						(ly:moment<? from currentmoment)
						(not (ly:moment<? to currentmoment))
					)
				)
				;%(display res)(newline)
			)
		)
	)
	res)))	

			%%%%%%%%%%% the main function %%%%%%%%%%%%%%%%%
extractMusic = #(define-music-function (parser location music from during) 
												(ly:music? ly:music? ly:music?)												
(let* (
	(fromlength (ly:music-length from))
	(duringlength (ly:music-length during))
	(tolength (ly:moment-add duringlength fromlength))
	)
(set! currentmoment (ly:make-moment 0 1 0 1))	;% global variable
(clean-Music
	(extract-Music music fromlength tolength ))
))

%%%%%%%%%%%%%%%%%%%%%%%%%%% tests %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\version "2.11.42" %% should work with 2.10

music = \relative{
	<<{c4 d e f g1}\\{c,2 c b1} >>
	g'4\< a b c\! 
	<<d1 \\ {b2\> b\! }>> 
	d4( c) b-. a-. 
	<<{g1-> g4-. f-. e( d)}\\{g4 f e d e2 r}>>
	c1}

 			
\score
{<<
	\new Staff {\music }  %% original
	\new Staff {R1*2
				 \extractMusic \music s1*2 s1*4   
					%% extract the music begining at the 2 measures and during 4 measures
				R1*2
	}
>>}  

%%%%%%%%%%%%%%%%%%%%%%