I check out the PDF manual. On the face of it it looks like a significant improvment.
The "strummaker live" type functions are still there on the green and blue zones of the keyboard, so you can manually trigger your up and down strokes. What looks like a big step forward is the chord variations on the black zone.
Key Switches
BLACK
Low octave (C0-B0) These key switches remotely control the Variation Knob, so you can
change from a major to a minor or diminished or whatever, so you have instant access to any
of 144 chords at any moment in your sequence.
C 0 = Major
C# 0 = Minor
D 0 = 7th
D# 0 = Minor 7th
E 0 = Major 7th
F 0 = Diminished
F# 0 =Augmented
G 0 = Sus 4
G# 0 = Bar
A 0 = Power Chord 1
A# 0 = Power Chord 2
B 0 = User Chord (actually, all chords in SM4 can be customized)
BLACK
High octave (C4-B4) These key switches control the Capo, or transpose function.
Just hit these keys and watch the capo move up the neck!
This overcomes a big limitation in Strummaker III were only 12 chords could be specified. Its a different approch to the chord detection methods used by Musiclab and Orange Tree but probably easire if you are not a keyboard player with a good knowledge of chord fingering.
It would be nice if Strummaker 4 could be used with ACC and Torch.