The QuadraVox algorithm is great for all kinds of pseudo-fingerpicking and added note effects; with or without constrained-to-scale pitch shifts.  Pick cleanly, limit your out-of-scale passing tones, and stick with octaves & fifths (or fourths) for simple 'chord' work.

In this preset, 4 additional notes ascend with equal spacing, from +2nd to +5th.  The far end of the expression pedal changes that note sequence from a 5th to an octave above.  Over the range of the EXP PED, the groups of notes will change together, but not perfectly in sync with each other.  That adds even more variety to the added note sequences.

Here, it's built around an E minor scale, and that works well with single note lines, dyads, and 'power chords'.  I like to adapt this technique to some of the more exotic scales available, and switch the directions around to fit the song context.  Pitch A,B,C, and D will be played in order, in alternating channels.  A+C on the left, and B+D on the right.

Pitch A Heel:  +2nd

Pitch B Heel:  +3rd 

Pitch C Heel:  +4th

Pitch D Heel:  +5th

Pitch A Toe:  +5th

Pitch B Toe:  +6th

Pitch C Toe:  +7th

Pitch D Toe:  +1oct