Audiomodern has released Random Riff Generator PRO - M4L. Random Riff Generator - PRO is a MIDI tool that generates MIDI sequences/riffs that can be sent to any synth software or hardware, sample, drum machine, anything that accepts a MIDI signal. It is intended to be a swiss army knife for creating random melodies sequences and musical riffs on the spot.
Random Riff Generator PRO has been designed to promote music creation both in studio and live with a simple and convenient user interface.
Features::

• Advanced random sequence & riff creator.
• Auto/Keyboard mode.
• Advanced Scale selector.
• Advanced quantization section.
• Octave selector.
• Save/Load and preset selector.
• Step & Loop section.
• The only available plugin of its kind.

Price: €19.
Video Demo

In the email I got it said this was for Max For Live - will this work in Sonar you think??
Nigel
 

I was thinking of getting this, but had the same question as you Nigel........it looks like it's only made for:
 
Ableton Live 8.1 & Max For Live 7.1 or higher is required..............
 
https://audiomodern.com/shop/max-for-live/random-riff-generator-pro/