GeoSonix is a free open source graphical music sequencer. It's now available for Mac and Linux and Windows.
The latest beta version (free and open source) is available for download from bitbucket.org/chrisgr99/geosonix/downloads Be sure to always choose to download the most recent version from the bitbucket site.
This example was created using three curves each with a different 32 beat rhythm pattern. Pitches are mapped from the cursor x position to 3.5 octaves of a minor pentatonic scale. Note velocities are on a four or eight beat cycle. For example the middle curve is on a cycle of [1,.85,.9,.85,.9,.7,.8,.7] where these number scale the velocity of a given beat vs the maximum velocity of 127.
Also used in this example is a new feature allowing notes in defined groups to be monophonic with respect to that group. In this example the notes on each curve is monophonic with respect to that curve. This allows legato playing where a given note is ended (if the duration timer has not already ended it) when another note on that curve starts.
The trumpet sounds are created in Ableton Live using the "Synth Brass - Analog Pad 2" patch.