MR

Today i was listening to a bootleg concert of the Paradise Theater tour recorded in Japan, probably listened to this recording dozens of times, but for some reason i noticed several instances where Dennis is busy playing piano and i heard synthesizers being played in the background-- mostly holding long continuous notes.
Specifically in Best of Times, Babe, Come Sail Away.
I know at times either JY or Tommy played background keyboards for brief sections of a song, however the synthesizer sounds i heard seem to be fairy lengthy, Best of Times is almost the last half of the song.
So my question is-- did Styx use backing tracks, was JY or Tommy playing these parts, was there someone off-stage, or are these synth sounds my imagination.
Looking forward to your thoughts.

As far as I know they have never used backing tracks. They have said several time that everything you hear at the concerts is played live.

Haven't they, in recent years, used a limited amount of tracks for "Mr. Roboto" (the robot "voices"), "The Outpost" (the drum machine) and maybe one or 2 other, specific songs?

Agreed though! - Never heard about them using tracks for vocals or instruments.