A mockup of how it might work under Windows:
1. User creates a MIDI clip called "Foo":

2. User creates a MIDI clip 'shortcut' by CTRL+SHIFT dragging "Foo" to the right (instead of CTRL dragging to do a regular copy). Both "Foo" clips now have some kind of reference/shortcut indicator on them to show they're symbolically connected (I've just used a red tab in the top right corner):

3. User removes some MIDI notes from the second "Foo" clip. These changes are reflected immediately in the first clip.

- This would work between session/arrangement view, and between different tracks.
- Clip 'shortcuts' could be turned into regular clips by consolidating them.
Does anyone else think this would be a killer feature?