Jam Session has a longer attack animation than Tremor, a long un-cancellable animation if you pull it off to the end, has a shorter range, needs to hit 10 times (if not more) to raise to SSS compared to two-three hits of Tremor, and the Style Meter actually drops down. Yeah, totally the same. Ever heard of context?
1 - It sure does, therefore it raises the meter even more effectively.
It also makes it less spammable. In the time it takes to throw a Tremor you are just starting a Jam Session.
2 - It's cancellable till the finisher, you can jump/sideroll/block/dash at any time before that last chord is struck. As I demonstrated, after hitting SSS you can simply get out of it and do other things freely.
I know, I was just pointing that out in case one wanted/happened to use the attack till the end.
3 - The amount of its does not matter, as pretty much any and all lesser enemies trapped in the attack, barring Greeds and a few others, will be stunlocked, completely unable to move, let alone attack.
What about DTed enemies, spiders and any enemy with a long range attack?
4 - Decaying meter is irrelevant to anyone perfectly capable of maintaining it.
And in DmC it doesn't matter even to those that can't maintain it, go figure.
5 - Have you ever heard of context?
Yes. The only thing that Jam Session and Tremor share is that both can raise the Style Meter to SSS very quickly. Properties, range, lenght of the attack and number of hits required are very different.
Maybe context isn't the right word (I'm italian, cut me some slack) but you should understand what I mean.
A better comparison would be with Drive, except that it doesn't raise have the Style-gain properties of Tremor.