brundlefly
As I mentioned, MIDI event start times and durations have to be modified to maintain absolute playback timing when the tempo (i.e. the ratio of timeline beats to absolute time in BPM without regard to audio/MIDI content) is changed. SM/BAN does that, and there's no reason the same algorithm couldn't be applied when a MIDI clip's timebase is set to Absolute. Obviously the writer of the Ref. Guide thought it would but didn't actually try it.

 
Probably so.
 
If you think about it - maintaining the start time is, IMHO, the only logical way to handle it. If you set five SM's, and then modify tempo somewhere just past the third one, SM's four and five would cascade shift in place, one, two, and three would remain in place. You can't modify the audio, how do you line all that up? You can't. Best to maintain the just start time, and at least you can set that to a specific MBT time.
 
If multiple areas of the audio must be keyed to specif MBT (and you wanna modify tempo again later), you gotta cut the audio into clips at each of those places, lock them to a specific MBT start time, and also you will need to manually time stretch/shrink those clips as needed to fix up any clip gaps or overruns as they are moved in (absolute time) relative to tempo changes. (It's what groove clip appears to do automatically).
 
 

SuperG
If you set five SM's, and then modify tempo somewhere just past the third one, SM's four and five would cascade shift in place, one, two, and three would remain in place. You can't modify the audio, how do you line all that up?

Yeah, you can't line it up in Sonar, but it would be pretty simple math to change the tempo after the "3.5" SM/BAN to keep "4" and "5" in place.  Sonar already figures out the correct tempo between 3 and 3.5.

Perhaps a variation of data locks?
 

stevec
If you think about it - maintaining the start time is, IMHO, the only logical way to handle it. If you set five SM's, and then modify tempo somewhere just past the third one, SM's four and five would cascade shift in place, one, two, and three would remain in place. You can't modify the audio, how do you line all that up? You can't. Best to maintain the just start time, and at least you can set that to a specific MBT time.
 

I'm not sure what you're saying here. In the case of SM/BAN the goal is to align the timeline to a recorded performance with tempo changes that match the changing tempo of the performance. If you wan't the audio to follow a manual tempo change, you can enable Audiosnap's Autostretch mode on it.
 
So with audio, it's your choice whether the audio follows a manual tempo change or not, but with MIDI you don't have the same flexibility; it's always going to follow a manually-entered tempo change.
 
The scenario in which I most often want the Absolute time option is actually when I've made the mistake of recording a freely played MIDI performance without a click into a project that has tempo changes in it from a previous session. Then I want to delete the existing tempo changes so I can use SM/BAN to align the timeline to the MIDI, but I can't because the MIDI will follow the removal of the existing tempo changes, and the original tempo of the performance will be lost. You can add tempo changes with SM/BAN, but you can't remove them and have the absolute timing of MIDI events preserved (except by Undo the same session).