Thanks for you request, but Alt-Up/Down has just been assigned to cursor-step-ignoring-increment. See thread:
http://www.aimoo.com/forum/postview.cfm?id=606458&CategoryID=361688&startcat=1&ThreadID=2581933There was also a different function in Impulse Tracker, where Alt-Up/Down would move the viewport without scrolling the cursor. This function will be added in v0.89.4, as Alt-Page Up/Down.
Note also, that shift is used in transposing too - Shift-Alt-Q/A to transpose in octaves.
All the best,
Chris