Tupac Estate -- A Million Bucks for Sex Tape Song Sounds GREAT!

Good news on the Tupac Shakur sex tape front ... Pac's estate has finally begun talks with a potential buyer ... but it ain't for the XXX part ... it's all about the music.

As TMZ first reported, an anti-hangover drink company called NOHO has offered to pay $1,000,000 for the rights to the unreleased song 2Pac was rapping along with ... while he was being "tended to" by a very friendly female in the 1991 footage.

Sources connected to the negotiations tell us ... the offer was big enough to catch the estate’s attention, because a rep for Pac's people reached out to NOHO and the two sides are trying to work out a deal.

There’s only one problem ... the estate doesn’t have possession of the sex tape and aren’t even sure which song is playing on it.

Oh yeah ... NOHO hasn't heard the song either -- but the CEO is banking on the fact that it's a Tupac song ... which means is has to be awesome.