"From This Moment On . . . Cole Porter," with Steve Lawrence and Eydie Gorme, will be so nice to come home to and oh, so easy to love, tonight at 10 o'clock on Channel 7.

This one-hour ABC musical special was produced by Gary Smith and Dwight Hemion and directed by Hemion, the team that last December gave television one of the best music specials in TV history, "America Salutes Richard Rodgers, The Sound of His Music," on CBS His show isn't quite that elaborate, but it's classy, attractive and inordinately enjoyable.

Once may not think of Lawrence and Gorme as our foremost practitioners of popular song - her vibrato can go hog-wild and his approach is awfully Las Vegas loungey - but they have obviously high regard for the dazzling Porter material, and they do anything but insult it.

The great moments, however, belong to guest stars Bob Hope and Ethel Merman, who recreate a moment from their '30s musical "Red, Hot and Blue" (which also starred Jimmy Durante). Later, Merman hosts a "swellegant, elegant" Porter party sequence that finds her yet again indomitable, wearing what looks like the curtain from Radio City Music Hall. What class, what pow and what pizzazz.

And when she joins Eydie for a duet, the market on zaftig showmanship has been cornered.

In addition, Natalia Makarova dances a mesmerizing medley of songs from Porter's "Can-Can," and the Yale Glee Club (from Porter's alma mater) joins for a thrillingly hokey rendition of "Night and Day."

ABC has not been promoting this show with the gusto it wastes on its usual bric-a-brac. The ratings may not be enormous. The Smith-Hemion "Richard Rodgers" spectacular did poorly in the ratings, losing even to the now-canceled "Nancy Walker Show." It's frightening to realize that without specials like this, music on network TV would be left entirely to the Donny and Maries and the Captain and Tenilles.

It thus becomes almost a duty and it remains entirely a fiesta to watch "From This Moment On . . . Cole Porter."