Hello dkala,
Alternation tool has a monophonic and a polyphonic mode.
Repetition tool is polyphonic.
Only the Legato Tool is monophonic, because the tool has to detect which intervalls you are playing on your keyboard.
If you want to play bass and melody line at once, you could set your sequenzer to multirecord (two miditracks), and setup individual playranges in the Legato tool. The only restriction is, the playranges don't have to cross each other.
A celli example:
you load the performance legato patch on midichannel one an two.
For channel one you set the playrange in the legato tool from c2 to f#3 (middle c = c4)
channel two from g3 to e5.
best wishes
Herb