It's claimed for these shows that on 4/25/69, "The Velvet Underground played a very long set and as a result the Dead only got to play one set on this date. According to Ramsey the Dead did the same thing to the Velvet Underground the next night.
I believe this is incorrect. The Dead opened on 4/25 and closed on 4/26. There is possibly also a missing second set from 4/25. Evidence: At the end of the Dead's set on the 25th, when the audience cries for more, Weir says, "We're gonna come back and do a second set in a little while, and we're gonna bring on two other real good bands, and they will blow your minds anyway; so we will be back in just a short while." (Which raises the question, what happened to the second set?) Doug Yule (Velvet Underground bass player) reports that the first night "the Dead opened for us we opened for them the next night so that no one could say they were the openers. As you know, the Grateful Dead play very long sets, and they were supposed to only play for an hour. We were up in the dressing room and they were playing for an hour and a half, an hour and 45 minutes. So the next day when we were opening for them, Lou says, Watch this. We did Sister Ray for like an hour, and then a whole other show." One Electric Theater audience member (Bob Reitman) says of a show that is probably the 26th, "I believe the Velvet Underground played first; then the Grateful Dead came out and played til about 2 or 3 in the morning. And literally, the only people left in attendance when the Dead were through playing were people that were laying on the floor. Eighty percent of the crowd had gone, and the Dead just kept on playing." Apparently the theater had no time restrictions, so the Dead seem to have been encouraged by the Velvets long noisy set on the 26th to play for even longer. My (unprovable) theory is that listening to that long Sister Ray is what gave the Dead the idea to close with a huge Viola Lee>feedback/WBOTB. They certainly didn't do anything like that at any other '69 shows.