Any of you guys got an idea what's going on with bars 2 and 3 on the lower staves? I'ts clearly some alternate way of scoring a trill which is what seems to be going on in the actual track

Go in around 5.50 for that round of 'dum-pen de-bat's, and it's over the 3rd 'de-bat' - it's just bugging me that it's using some scoring system I'm not familiar with, like what's with the incomplete beams on notes? also, am I supposed to trill the entire chord against the lower note!

Btw I am not totally playing all the instrument parts here, most of it is easy enough to put all the 4 vocal parts on left hand with a bit of inversion going on, if I can't get both of the piano parts on right hand I drop the least interesting bit and figure I'll come back and pick it up on pedalboard once I've learned the rest of the piece.
If only we knew a friendly Italian who loves synths.
