In a career devoted to pushing the boundaries of popular taste, rapper Ice-T really has his hands full this time.

The godfather of gangster rap is among seven acts on the Lollapalooza tour, which arrives Saturday at the World Music Theatre. On the surface, at least, he`s the outsider on a bill that also includes the art-metal bands Jane`s Addiction and Living Colour, British gloom-popsters Siouxsie and the Banshees, industrial dance-machine Nine Inch Nails, the punkish Rollins Band and renegade grunge rockers the Butthole Surfers.

It`s virtually unprecedented for a rap performer who appeals to the hardest core of the largely black inner-city audience to share a stage with rock and pop bands that have a primarily white following, especially on such a large scale-the Lollapalooza tour is playing 21 cities nationwide, with audiences of 20,000-plus expected at most shows.

But Ice-T says he doesn`t feel out of place.

''I`m not a traditional black rapper, because I`m too hard for most black audiences,'' he says. ''I feel perfect out there with the Butthole Surfers, because I know where they`re coming from. I know where Henry Rollins is coming from because I used to watch (Rollins` former band) Black Flag back in the punk and hard-core days. I`m into Nine Inch Nails because I`m a big Ministry fan, which does a similar kind of music.''

Last year, Ice-T appeared in two West Coast shows billed as the Gathering of the Tribes, in which he was the sole rapper among rockers such as Iggy Pop, the Cramps and Soundgarden.

''The promoters were scared to death, because they thought when I got on stage people were gonna boo,'' he says. ''But we tore it up. We had people standing and yelling, cause rock groups don`t say, `Throw your hands in the air,` and `Go ahead, scream!` People had a good time, so I think that was the real breakthrough that showed this kind of thing can work if you use the right rapper.''

Since then, the merging of rock and rap, ''white'' and ''black'' music, has become more commonplace on record, including collaborations between major artists such as R.E.M. and KRS-One (''Radio Song''), Sonic Youth and Chuck D. (''Kool Thing'') and Anthrax and Public Enemy (''Bring the Noise''). Concerts matching rap and rock groups, such as the Sisters of Mercy/Public Enemy bill at Poplar Creek Music Theatre a few weeks ago and the Sonic Youth/ Public Enemy show at the Aragon Ballroom last December, also have been popping up more frequently in the last year.

''Rap and rock are the exact same thing,'' Ice-T says. ''Rap groups like Public Enemy are hard-core about music. We`re creating the same energy that rock `n` roll creates, so any audience can relate.

''The way I define music is if you`re dealing with the system and you`re just floating with it singing about milkshakes, love and homework, then you`re doing pop music. But if you rock the system, you`re rockin` and rollin`, whether it be reggae, jazz, rap, whatever.''

Ice-T makes the point even more explicitly on his recent album, ''O.G. Original Gangster'' (Sire), which contains a wailing, heavy-metal cut, ''Body Count,'' by a black hard-rock trio of the same name, with Ice-T on lead vocal. Body Count was recently signed to a record deal by Sire Records, with Ice-T as the lead vocalist. The rapper will open his portion of the Lollapalooza concert with a rap performance, and then bring on Body Count to back him up for three songs.

''These guys are my homeys (friends) from Crenshaw (High School)'' in South Central Los Angeles, Ice-T says. ''They would always be fighting with me about making a straight-up rock record and I`d be telling them you can`t do it right now, because the rap audience wasn`t buying my records to get rock. So we`d tease the audience with it, just give `em hints of rock on each record, but never full out.''

Lollapalooza and Body Count are just the latest in a series of adventurous artistic steps taken by Ice-T. Most of them have paid off: His spacious split-level home that overlooks Sunset Boulevard is only a short distance from the ''killing fields'' of South Central that he grew up in, but he no longer has to hustle to make a living. His previous three albums have each sold at least 500,000 copies and ''O.G. Original Gangster'' recently cracked the Billboard top 20.

But that former life of hustling, shooting, pimping and drug-dealing haunts Ice-T still, and has been the basis of virtually every one of his records since ''Six in the Morning'' in 1987, generally acknowledged as the blueprint for the ''gangster rap'' style.

''The whole crew I was running with, all of `em went to prison, and two of `em got life terms,'' he says. ''I was the only one who missed the tag. We used to rob jewlery stores, pull kidnappings, anything to make a buck. I was very lucky to be detoured just in time.''

The cover photos on his latest album are a reminder of how thin that line was. One shows the bejeweled, tuxedo-clad rapper standing in front of his Ferrari. In the other, he is scowling in a T-shirt and jeans, chained at the wrists.

''The more success I get, the more guilt I feel about the homeys that are stuck,'' he says. ''You never lose that core. It`s like asking a Vietnam veteran if he can still tell you about a firefight. My boys are still dying out there, and they keep telling me, `Yo, Ice, kick it, keep tellin` `em.` '' And tell it he does, in more vivid detail and harsher language than almost any rapper in the business. His baritoned delivery is more measured, more ominous than verbal gymnasts such as Rakim or L.L. Cool J, and whereas records by N.W.A. or Public Enemy blast the funk, Ice-T`s music seems to ooze menacingly from the speakers.

''I don`t make records that you can dance to, they`re more for people to kick back, have a cold drink, and trip. They`re like vocal novels,'' he says. ''When I started out, I had lots of rhymes about stealing and hustling and living the life, but I thought that to get over (to a wider audience) I would have to rap like Run-D.M.C. and L.L. Cool J.

''L.L. was rapping about radios (`I Can`t Live Without My Radio`), but I didn`t know anything about carrying a radio around. We were stealing radios. So I wrote `Six in the Morning,` which was just about a kid trying to run from the cops, just that whole (expletive)-the-police attitude. Another cut was

`Pain,` about how cops broke my face with an ax. Once that hit, I knew that I would be making records till the end of time, because all I had to do was rap about what I knew.''

What Ice-T knows has expanded immeasurably over the years, and his records reflect that growth. While his imitators and disciples, including N.W.A. and the Geto Boys, have eclipsed him as the hardest of the hard-core by taking gangster rap to even wilder and more pathological extremes, ''O.G.''