mplay   macro

(define-macro (mplay . args)
  (if (symbol? (car args))
      `(play-midi-note (*metro* beat) ,(car args)
           (real->integer ,(cadr args))
           (real->integer ,(caddr args))
           (*metro* 'dur ,(car (cdddr args))) 0)
      `(play-midi-note (*metro* (+ beat ,(car args))) ,(cadr args)
           (real->integer ,(caddr args))
           (real->integer ,(car (cdddr args)))
           (*metro* 'dur ,(cadr (cdddr args))) 0)))