Radium

Radium is a music editor of the "tracker" family. Trackers are sequencers that display music data on a vertical, top-down list of notes and effects data.

From the Radium website description :

Compared to the normal sequencer interface editing is quicker and more musical data fits on the screen.

• Compared to trackers, note positions and effects are edited graphically, which should be quicker, provide more vertical space and give a better musically overview.

However, despite its unusual appearance, it's a design goal for Radium to be straightforward to use, and easy to learn. It should not be harder to learn Radium than any tracker or most midi sequencers.

Some Features

• Velocity automation
• Effect automation
• Pitch automation
• Tempo automation
• Smooth scrolling
• MIDI sequencing
• Optional piano roll
• Tickless.
• Modular mixer.
• LADSPA and VST plugins
  (More than 100 LADSPA plugins are included in the OSX and Windows versions)
• Several built-in effects and instruments
  (virtual instruments, etc.)
• Pure Data embedded.
  (Linux only for now)
• Zooming
• Microtonality
• Perfectly tuned default color scheme
• Extension language support.
  (Write programs that generate music or modify your songs)
• Scores can be generated with Common Music Notation (CMN)
• Open source