Background:

OM version 4.0.31432, introduced the new alternative pipeline syntax (https://opusmodus.com/forums/topic/4014-using-arrows-package-in-om-threading-macros-pipeline-syntax/).

Benefits:

Depending on personal taste (tolerance for nesting) the new alternative pipeline syntax may

• simplify coding during iterative development and

• make longer code pipelines easier to read and comprehend.

Example:

Here is a first OM canonical example (taken from OM docs), contrasting standard LISP vs pipeline syntax.

See code for bass and section below.

Standard LISP Syntax:

;;;; START === Standard LISP Syntax ================
;;;;
;;;; Source: OM - Score Examples - Jazz - Blue Mount.opmo
;;;;
;;---------------------------------------------------------
;; Blue mount
;; Jazz style generator
;;---------------------------------------------------------

;; Library definition for Bassline motives 
(def-library JBass1
             (:section jb8tps
              jb0 (length-span '2/1 '(q. c2 mf q. c3 f q g2 mf e eb2 p
                                         f2 fs2 mp g2 eb2 f2 mf g2))
              jb1 (length-span '2/1 '(e c2 f - - q c2 e g1 mp a1 mf bb1 f))
              jb2 (length-span '2/1 '(q. c2 f g2 mf q c3 q. c2 f g2 mf q d3))))

;; Library definition for left hand piano motives
(def-library JPianoMg4th
             (:section jp8tps
              jp0 (length-span '2/1 '(-e q c3f3b3 - s d3g3c4 e3a3d4
                                         -e g3c4f4 -q f3b3e4 - -))
              
              jp1 (length-span '2/1 '(e d3g3c4 q g3c4f4
                                        -e e3a3d4 f3b3e4 -h))
              
              jp2 (length-span '2/1 '(-e q b3e4a4 a3d4g4 -q s e3a3d4
                                 f3b3e4 -e f3b3e4 -q))))

;; Library definition for drums patterns
;; (from midi to score Opusmodus option)
(def-library StudioTightKitPttn
             (:section stkp8tps
              stkp1 '(s c2fs2 -s fs2 - e2fs2 - fs2 f3
                        c2fs2gs2 - s fs2 - e2fs2 - c2fs2 -s)
              
              stkp2 '(s c2fs2 -s fs2 - e2fs2 - fs2 f3
                        c2fs2 a3 e2fs2 -s e2fs2 -s g3 d2)
              
              stkp3 '(s c2fs2cs3gs3 -e s d2 fs2 e2
                        f3gs3e3 -e -s fs2 -s fs2 - d2fs2 e2)
              
              stkp4 '(s c2fs2cs3gs3 -e s d2 fs2 -
                        fs2f3gs3 -e s a3 e2 - e2 - g3 d2)))

;; Modal harmonic path
(setf path (tonality-series 
            '(dorian dorian lydian dorian mixolydian aeolian)
            ;'(bebop-dominant)
            :root '(d4 d4 f4 d4 g3 a3) :map '(octave)))
            ;:root '(a3)))

;; Generation of bass line
(setf bass1 (library 'JBass1 'Jb8tps nil :random 8)) 

;; Transposition of bassline
(setf bass1.transp (pitch-transpose 12 bass1))

;; Map to harmonic path     
(setf bass1.omn (tonality-map path bass1.transp))

;; Motivic choice in library for lef hand and tonality mapping
(setf pianomg1.omn
      (tonality-map
       path (library 'JPianoMg4th 'jp8tps nil :random 8)))

;; Pitches for right hand melody improvisation
;; Vector for melodic contour for Right hand
(setf vector (vector-smooth 0.12 (gen-noise 1024)))

;; Map vector to pitch
(setf pianomd1.p (vector-to-pitch '(d3 d6) vector))

;; Length based on binary-change
(setf pianomd1.l
      (length-span
       (get-span bass1.omn)
       (binary-to-length (gen-binary-change pianomd1.p))))

;; OMN assembly for right hand and tonality mapping
(setf pianomd1.omn
       (tonality-map
        path
        (make-omn
         :pitch pianomd1.p
         :length pianomd1.l
         :velocity (pitch-to-velocity 'mp 'f pianomd1.p))))

;; Processing of the right hand, tie repeated pitches.
(setf pianomd1.omn.p (filter-tie pianomd1.omn))

(setf drums1.omn
      (gen-repeat 
       4 (append
          (library 'StudioTightKitPttn 'stkp8tps 'stkp1 :repeat 3)
          (library 'StudioTightKitPttn 'stkp8tps 'stkp4))))

(def-score BlueMount
    (:key-signature '(c maj)
     :time-signature '(4 4)
     :title "Blue mount"
     :tempo 132
     :composer "S.Boussuge"
     :copyright "Copyright © 2013 S.Boussuge"
     :layout (list
              (piano-layout 'pianomd 'pianomg)
              (bass-layout 'bass)
              (bass-layout 'drums)
              ))
  
  (pianomd
   :omn pianomd1.omn.p
   :channel 1 
   :sound 'gm
   :program 'Acoustic-Grand-Piano
   :pan 82)
(pianomg
   :omn pianomg1.omn
   )
(bass
   :omn bass1.omn 
   :channel 2 
   :sound 'gm
   :program 'Acoustic-Bass
   :pan 42)
  
  (drums
   :omn drums1.omn
   :channel 10
   :pan 64))
;;;; END === Standard LISP Syntax ================

---

Pipeline Syntax:

;;;; START === Pipeline Syntax ================
;;---------------------------------------------------------
;; Blue mount
;; Jazz style generator
;;---------------------------------------------------------

;; Library definition for Bassline motives 
(def-library JBass1
             (:section jb8tps
              jb0 (length-span '2/1 '(q. c2 mf q. c3 f q g2 mf e eb2 p
                                         f2 fs2 mp g2 eb2 f2 mf g2))
              jb1 (length-span '2/1 '(e c2 f - - q c2 e g1 mp a1 mf bb1 f))
              jb2 (length-span '2/1 '(q. c2 f g2 mf q c3 q. c2 f g2 mf q d3))))

;; Library definition for left hand piano motives
(def-library JPianoMg4th
             (:section jp8tps
              jp0 (length-span '2/1 '(-e q c3f3b3 - s d3g3c4 e3a3d4
                                         -e g3c4f4 -q f3b3e4 - -))
              
              jp1 (length-span '2/1 '(e d3g3c4 q g3c4f4
                                        -e e3a3d4 f3b3e4 -h))
              
              jp2 (length-span '2/1 '(-e q b3e4a4 a3d4g4 -q s e3a3d4
                                 f3b3e4 -e f3b3e4 -q))))

;; Library definition for drums patterns
;; (from midi to score Opusmodus option)
(def-library StudioTightKitPttn
             (:section stkp8tps
              stkp1 '(s c2fs2 -s fs2 - e2fs2 - fs2 f3
                        c2fs2gs2 - s fs2 - e2fs2 - c2fs2 -s)
              
              stkp2 '(s c2fs2 -s fs2 - e2fs2 - fs2 f3
                        c2fs2 a3 e2fs2 -s e2fs2 -s g3 d2)
              
              stkp3 '(s c2fs2cs3gs3 -e s d2 fs2 e2
                        f3gs3e3 -e -s fs2 -s fs2 - d2fs2 e2)
              
              stkp4 '(s c2fs2cs3gs3 -e s d2 fs2 -
                        fs2f3gs3 -e s a3 e2 - e2 - g3 d2)))

;; Modal harmonic path
(setf path (tonality-series 
            '(dorian dorian lydian dorian mixolydian aeolian)
            :root '(d4 d4 f4 d4 g3 a3) :map '(octave)))

;; Bass
(setf bass (-<>
            (library 'JBass1 'Jb8tps nil :random 8)
            (pitch-transpose 12 <>) ;; Transposition of bassline
            (tonality-map path <>) ;; Map to harmonic path     
            ))

;; Piano left hand
(setf piano-left-hand (-<>
                       (library 'JPianoMg4th 'jp8tps nil :random 8)
                       (tonality-map path <>)
                       ))

;; Piano right hand
(setf piano-right-pitch (-<>
                         (gen-noise 1024) ;; Vector for melodic contour
                         (vector-smooth 0.12 <>)
                         (vector-to-pitch '(d3 d6) <>) ;; Map vector to pitch
                         ))
(setf piano-right-length (-<>
                          (gen-binary-change piano-right-pitch) ;; Length based on binary-change
                          (binary-to-length <>)
                          (length-span (get-span bass) <>)
                          ))
(setf piano-right-hand (-<>
                        (make-omn :pitch piano-right-pitch ;; Assemble omn
                                  :length piano-right-length
                                  :velocity (pitch-to-velocity 'mp 'f piano-right-pitch))
                        (tonality-map path <>)
                        (filter-tie <>) ;; tie repeated pitches
                        ))

;; Drums
(setf drums (-<>
             (library 'StudioTightKitPttn 'stkp8tps 'stkp1 :repeat 3)
             (append <> (library 'StudioTightKitPttn 'stkp8tps 'stkp4))
             (gen-repeat 4 <>)
             ))

;; Score
(def-score BlueMount
    (:key-signature '(c maj)
     :time-signature '(4 4)
     :title "Blue mount (modified pipeline syntax)"
     :tempo 132
     :layout (list
              (piano-layout 'piano-right 'piano-left)
              (bass-layout 'bass)
              (bass-layout 'drums)
              ))
  
  (piano-right
   :omn piano-right-hand
   :channel 1 
   :sound 'gm
   :program 'Acoustic-Grand-Piano
   :pan 82)
  (piano-left
   :omn piano-left-hand
   )
  (bass
   :omn bass
   :channel 2 
   :sound 'gm
   :program 'Acoustic-Bass
   :pan 42)
  
  (drums
   :omn drums
   :channel 10
   :pan 64))
;;;; END === Pipeline Syntax ================

Meanwhile a much better pipeline syntax was introduced to OM by @opmo with ˋbind-indexˋ, see https://opusmodus.com/forums/topic/4133-opusmodus-4031506-update/#comment-14316.

It offers the feature to be able to refer to intermediate results, which is a great thing in more involved pipelines.