Hair Band LEGENDS Unite to Honor Jani Lane

Some of the biggest hair bands you haven't heard from in 20 years are REUNITING in Los Angeles next weekend ... all to pay tribute to their fallen comrade Jani Lane ... and they're doing it for free.

Great White, Quiet Riot, LA Guns, Enuff Z'nuff and Slammin' Gladys are all set to perform at the Key Club in Hollywood -- and we're told Lane's family will be there.

300 FREE tickets will be given out at the Key Club box office starting at 10:00 AM.

Lane -- the former lead singer for the rock band Warrant -- died last week at an L.A. hotel. Officials have not released his official cause of death.