anchor.diff:        (pushword (label :seq-end))
         (pushword (label :seq-start))
         (jsr 'player-load)
  -      
         (rts))
   
       (write-song-data-for-reg-player (funcall continuation) :seq-start :seq-end)
  
positive.code:         (lda mptr-msb)
          (cmp (zp (1+ endptr)))
          (asif :equal
            (when t ;;break-at-end, FIXME/TODO
              (brk)
               (db #xF1)
               (rts))
            (poke (zp startptr) mptr-lsb)
            (poke (zp (1+ startptr)) mptr-msb)))
  
        (rts))
  
  
negative.code:       (defun ,(intern "NSF-OUTPUT-FILE" package) (filename)
          (generate-nsf-preview ,name #',asm-fn-name :filename filename)))))
  
  (defun emit-fixed-cycle-player (context var-base &key break-at-end)
    "Emit fixed-cycle player routine. Requires VAR-BASE specifies 8 bytes of adjacent zeropage storage."
    (check-type var-base (integer 0 250))
    (let* ((*context* context)
  