When you freeze a track, S1 freezes the entire track. It is ok with a completely different pattern. However, if the track is a kinda repetitive one such as rhythm guitar, it's a waste of space. Bouncing a track eats most of the room in your hard drive. Instead, you can have S1 bounce the only single item and put it in the same spot. It's hard to explain, so I'll give you an example.
eg) You made a simple repetitive rhythm guitar track in 4 bars. You duplicated it for the entire track. The entire track is almost 3 mins. If S1 bounces only the first part and automatically duplicates it for the rest of the parts, only a single file will be generated.
Hope we can see this feature in the next update.
