I tried lengthening Another Day by Dream Theater from 4:26 to 8:00.

I set it to avoid the segment that the key changes and to favor the 2 solo segments.

It doesn't seem like its doing a good job. Only the first 5 seconds of the intro made it and then is just repeating over and over the big solo. In the end, a very small part of the short solo makes it in as an outro.

Maybe it works better at shortening songs or maybe changing duration closer to the original duration.