A "Jimmy Stewart" is what Umphrey\'s label an improvised jam of a song. They call it a "Jimmy Stewart" instead of , let\'s say, "Nothing Two Fancy", because the improvised section is drastically different from the song\'s theme. It\'s usually built on a riff/theme/chord progression. Most of them fall extremely short IMO. It usually takes them a long time to find an interesting chord progression, and then instead of building on that, they usually switch to something different. I merely took these improvised pieces and gave them different names. Regardless, you should download it.