Heart's "Brigade," one of the year's fastest-rising albums, is already No. 4 on the Billboard pop chart after just a month in release. It may be the next No. 1 album, possibly squeaking past the other strong candidate for the top spot, M.C. Hammer's "Please Hammer Don't Hurt 'Em" (No. 2). Sinead O'Connor still tops both pop charts with her album, "I Do Not Want What I Haven't Got," and her single, "Nothing Compares 2 U." Other fast-rising albums: the "Pretty Woman" sound track (No. 11), Public Enemy's "Fear of a Black Planet"(No. 12), Fleetwood Mac's "Behind the Mask" (No. 22) and Suzanne Vega's "Days of Open Hand" (No. 53).