There appears to be an issue in omitting dyads (chords) in the notation viewer when attaching attribute 'ped, as in this example:
'((q c4 e3e4 ped) (q g3 c3c4 ped h e4 ped) (q c4 ped g4 e4e5 ped))
Similar issues occur when using the attribute-series function:
(setf mat '((q c4 e3e4) (q g3 c3c4 h e4) (q c4 g4 e4e5)))
(attribute-series '((- 1) (ped 2) (ped 4) (ped 1)) mat)