My most vivid concert memory is pretty easy to choose. As a prelude, you should know that a large group of us in the northern Buffalo, New York, area were into Gentle Giant in a big way. A station wagon full of us visited a friend attending Columbia University in NYC for the weekend of a Manhattan Gentle Giant concert after In a Glass House (my personal favorite Gentle Giant album) came out. Gentle Giant was headlining and the crowd was rocking. At one point Ray stopped during a violin solo (I think it was during Plain Truth), and some guy up front screamed. Ray put down the violin and screamed back at him. Then the whole crowd and Ray started a screaming back at each other before he cranked out the rest of the solo. Needless to say the ovation was long and well-deserved for that number.
Soon after (Fall 1975 or Winter 1976), Gentle Giant was booked in Buffalo as the backup band for Alvin Lee's african-influenced post-Ten-Years-After band -- why, we'll never know. We got in line early and grabbed the entire center 7th and 8th row of Kleinhan's Music Hall (with symphonic quality acoustics). We were psyched! We were early and milling about the stage when Gentle Giant was setting up, and a few of us got unexpected sets of autographs! After the first couple of songs it became evident that, as the review in the paper stated, "a phalanx of Gentle Giant freaks were up front giving standing ovations," while the rest of the crowd didn't know how to handle it. I was on the edge of my seat when Ray started the same violin solo that I had just seen in NYC, and when the pause came I jumped up and screamed -- all by myself in a nearly silent music hall. Ray looked at me and screamed back. Then the two rows of us stood and screamed as one unit back and forth with Ray. We were jumping and jiving and dancing and didn't sit down until the next song started.
It was a bittersweet concert event. They were completely unappreciated by the rest of the audience and didn't come back for a single encore in spite of the two rows of us screaming ourselves hoarse even after the lights came on. The acoustics were wonderful and the effort by the band had been evident, but "you can't make 'em drink..." Alvin Lee's (gratefully short-lived) band was simply awful, and the two rows of us stood up after the second set and filed out to the bar downstairs to discuss the great show we took in. It was like they had been playing just for us. The reviews the next day were all pro-Gentle Giant so we felt vindicated. I saw Gentle Giant many times before and after that, and that (fortunately) was the only time I saw them mistreated, but it was a concert like no other.