WARNING: PART BASS Hard has the same amount or more notes than Expert.
I've charted a couple songs and used CAT reductions successfully on those, but on my recent song, the Hard parts are the same as Expert on Drums, Guitar, and Bass. A few exceptions with guitar: it does simplify 3-note chords into 2-note chords, for one thing. Also on drums, it doesn't simplify any verses or the chorus, but it simplifies just before the verse, and a fast part during the end of the bridge.
Medium and Easy charts seem to have reduced just fine.
Any idea what's going on? Thanks!