Sunday was a day of conspicuous compassion: While millions of Americans were participating in Hands Across America, an estimated 10 million people worldwide were participating in Sport Aid's Race Against Time. Ironically, this pitted the two major masterminds of famine philanthropy, Ken Kragen of USA for Africa and Bob Geldof of the Band Aid Trust, against each other. In America, only 50,000 people participated in Sport Aid, including 4,500 who took part in the New York race. But similar races were held in 278 cities in 78 countries on five continents, with organizers hoping to raise $100 million for the starving in Africa. In London, 130,000 people signed up to participate in the six-mile run through town; in Bangkok, 25,000 raced; in Budapest, 10,000 runners participated, in the biggest race ever staged in Hungary. And while Hands Across America received limited television coverage outside of news broadcasts, satellite coverage of Sport Aid races in 13 countries was beamed to 50 countries and an estimated 700 million viewers.

Geldof, meanwhile, has just published his autobiography in London. The 350-page book "Is That It?" is getting rave reviews for its typically rude appreciation of the business and politics of rock 'n' roll and for Geldof's unflinching appraisal of his own position in rock and its philanthropic offshoots. Geldof also is going into the studio to record his first solo album with producer Dave Stewart of Eurythmics; the finished product is expected in the fall. Geldof's group, the Boomtown Rats, had been dropped by its record label for lack of sales. 'Porn' Hearings Can Be Seen

If you want video highlights of the "porn rock" hearings on Capitol Hill to accompany the transcripts available from the Government Printing Office, they are available from C-Span, the cable channel that carried the hearings live. All five hours are available, as well as hour-to-hour segments (the cost is $100 per hour). If you identify whom you'd like to have -- Frank Zappa, Dee Snider, John Denver or the minister whose lyric recitation was the most explicit part of the proceeding -- CNN should be able to isolate that hour. Write to Corporate Development, C-SPAN, 400 North Capitol St., Washington, D.C. Seems Like Yesterday

Motown Records, which recently released an intriguing album of previously unheard Marvin Gaye songs, will celebrate the 25th anniversary of the Supremes with a three-record set, "The Diana Ross and the Supremes 25th Anniversary." The set features 20 top-20 hits as well as the Supremes' first sessions at Motown, a 1961 Smokey Robinson song ("Those Deejay Shows"), a 1963 song written and produced by label head Berry Gordy Jr. ("Come On, Boy") and a 1965 Coke commercial to the tune of "Baby Love." Among the unreleased tracks are four more Robinson tunes, a quartet of Holland-Dozier-Holland songs and "Penny Pincher," a 1963 song originally supposed to follow up "When the Love Lights Start to Shine"; instead Motown released "Where Did Our Love Go?" and the rest is pop music history. Video Challenge to Filmmaking

The most striking new video to hit the small screen in some time is Peter Gabriel's "Sledgehammer." "I'll do anything you need," Gabriel sings. The video, which took six days to shoot, is an essay in transformation; the five-minute piece was shot two frames at a time, with Gabriel doing 3,000 poses and being subjected to more changes than a Democratic platform (a favorite: his emergence as a fruit salad). Directed by Steven Johnson, with special effects by Tom and Stephen Quay, "Sledgehammer" is an example of a rock video offering some of the best, most clever filmmaking around -- and reaching the kind of audience experimental films never find. Monthly Schwann to List CDs

Schwann, the easy-access bible for record retailers and consumers, has decided to replace its monthly record and tape catalogue with a compact disc catalogue, effective in July. Coverage of new albums will be limited to new releases and deletions, and for cassettes, solely to new releases. Schwann catalogues have previously contained listings of active LPs and cassettes (these catalogues will be published in June and October, and intermittently thereafter). Despite the continuing emergence of CDs in the marketplace, some critics see Schwann's move as premature, suggesting it will only hurry along the demise of the album format, even as it hurts the dominant cassette market. For larger retailers, the huge and unwieldy Phonolog is the prime catalogue resource, but the Schwann, the size of a small paperback, has long been the favorite ready-reference tool.