Isn’t there a tool that lets you rescale pattern data by certain ratios? Then you can work with relativity…
No need to be Einstein to do that! For the 150bpm passage in 100bpm song, you would scale the passage to 100/150 = 2/3 of the original length.
You mean this one?
https://forum.renoise.com/t/new-tool-2-8-3-0-flexible-pattern-resizer/30664