5/18 1:18 PM PT -- Tinsley tells us, "I will defend myself against these false accusations. I can only assume the motivation for the lawsuit filed against me. These accusations have caused embarrassment for my family, my friends and my fans. I will fight both in and out of court to repair the damage that has been done."

Boyd Tinsley, the former Dave Matthews Band violinist, has been sued by a man who says Boyd sent him disgusting, sexually suggestive texts, and even masturbated next to him when he was sleeping.

James Winn claims in a new lawsuit, obtained by TMZ, he was a street musician in San Francisco when Tinsley discovered him in 2007, when he was 18. Winn says Tinsley created a boy band called Crystal Garden. Winn was the trumpet player in the band.

Winn says things turned really bad in 2015, when Tinsley allegedly started flirting, sexting and physically touching him. Winn claims in 2015, he bought 5 tickets to a sporting event for Winn, saying, "Man, you better suck my d*** or something."

In another instance, Winn says the same year they were working on music in Tinsley's living room when they both got tired. Winn says Tinsley began touching him on his leg, putting his feet on his butt and rubbing his back. Winn says he fell asleep and woke up horrified to see Tinsely ejaculating right next to him, rubbing his penis with one hand and Winn's butt with the other.

Winn claims a week later Tinsley texted, apologizing and saying he was "messed up" and he had "confused his pills."

And there were other texts, Winn claims. In one, Tinsley allegedly wrote, "You're such boner material and I want you at your best. I'm actually masturbating to the thought of your shots." It goes on ... "prob will have you shave your pubes, at least above the c*** base."

Tinsley took an indefinite break from the Dave Matthews Band in February, when rumors of the allegations began to surface, saying he needed to focus on his family and health.