Mike's sister, Melinda Starr, tells us everyone is gathering around International Fountain -- next to the Space Needle -- where a water show is usually set to classical music ... but for the memorial it'll be rocking to Alice in Chains tunes.
Melinda says officials at Seattle Center offered to change the music for the memorial -- and adds Seattle Police are providing security, free of charge.
Starr was found dead earlier this month in Salt Lake City.
Melinda says some of Mike's old Alice in Chains mates will also be at the tribute -- which is open to the public and begins at 4:00 PM.
