Because of considerations such as synchronized video, programmed backing tracks, precision pyrotechnics/lighting and click-tracks, a lot of touring concert acts have to do the same set each night. To shake it up — to engage in any spontaneity or free-form improve whatsoever — would ruin the PRESENTATION, and God knows we can't have that.

I'm not sure I expected this sort of thing from pioneer metallurgists Black Sabbath, who, in their 48th year, on what probably really is their farewell tour, play Saturday in the Mohegan Sun Arena. But that's apparently what's happening inasmuch as a casual online check of their set lists indicates no variation at any stop.

Wouldn't you sorta want to go out joyously and go a little crazy?

Ozzy: "Hey, Tony and Geezer! What the hell! For old time's sake, let's play 'Supernaut'! Or how about 'Killing Yourself to Live'?"

Tony and Geezer (together): "Fabu idea!" And they'd crank into one or the other or both and maybe it'd be a little rusty and maybe not but fans would go nuts for the rarities ...

For the record, the Men of Sab are performing four songs from the self-titled first album, six (of eight) from "Paranoid," three from "Masters of Reality," one from "Vol. 4" and one from "Technical Ecstasy." None at all from "Sabotage" or "Never Say Die!" and, heinously, none at all from their masterpiece, "Sabbath Bloody Sabbath." Nothing, of course, from the Dio years.

So now you know.

Black Sabbath with Rival Sons, 7:30 p.m. Saturday, Mohegan Sun Arena; $94-$194; 1-888-664-3426.