How many recording artists have released live albums since Peter Frampton's "Frampton Comes Alive" earned more money than any other rock album in history?

Before you spend the next few days listing them all (did you name the Michael Stanley Band? How about Don McLean?), suffice it to say that the output of live recordings is substantially more now than in previous years.

This suggests that the sales of "Frampton Comes Alive," and the unexpected success of the three live singles from the album, have prompted performers to follow the leader and run tape during all their concerts. Half true.

It is not the performers who insist upon live product as much as their employers. Live albums, generally, are pauses - a way for artists to keep their visibility and fulfill contractual obligations without having to work out new material.

Many record companies now feel the best way to market their artists is to present them live. (In all fairness, it should be mentioned that record company executives are not exactly standing over their musicians with clubs. Many acts agree to do live albums in their contracts. Others feel they are naturally better in concert than in the studio. The weight of the decision lies with the act, though industry types do offer strong advice.)

Two performers who have recently released live music offer evidence that "live" often is the best way to exhibit their wares. Their situations have some common ground: Both players are striving for broader commercial acceptance; both of their new packages are two-record sets; and both record for A&M Records, the company that cleaned up on Peter Frampton. For all that, they differ dramatically in their individual presentations.

"It Is Time for Peter Allen" (A&M SP 3706) should prove a prophetic title. Allen has commanded star status in New York and Los Angeles for years but never has fared particularly well anywhere else.

One reason for this is that Allen is one performer who must be seen to be fully appreciated. Also, despite some mild overtures to the rock audience, he is ostensibly a cabaret singer and it is to that crowd that "It Is Time . . ." cleverly includes much of the stage patter and humor that makes Allen so endearing. Music, though, not patter, is the point.

The performance opens with "Love Crazy," a concert staple but not heard on vinyl until now. From there on, it's a typical Allen production.

Jaunty but meaningful compositions like "She Loves To Hear the Music" and "Continental American" alternate with moving ballads including "Quiet Please, There's a Lady on the Stage" (written for his former mother-in-law Judy Garland) and "Don't Cry Out Loud." There are his best-known tunes: "I Honestly Love You," which won a Grammy for Olivia Newton John ("She got a gold statue and I got a certificate"), "I Go to Rio" and "The More I See You," and some new songs like "Interesting Changes."

The set is energetic and emotional and imbues the listener with a sense of participation. You can't ask more from a live album than that.

It is generally agreed that the best album Nils Lofgren ever did was his "radio-station-play-only" live bootleg "Back It Up," which never made it to the record store shelves. Lofgren attempts to correct that mistake with "Night After Night" (A&M Sp 3707) and he nearly succeeds.

The album, like Allen's, has parts recorded at the Roxy, but the majority of the performances took place in England and Scotland, where Lofgren is a major attraction. His supporting band here (David Platshon - drums; Rev. Patrick Henderson - keyboards; Wornell "Sonic Prince" Jones - bass; and brother Tom Lofgren - guitar and organ) is not as strong as on "Back It Up," but Lofgren has included new live versions of that song and Carole King's "Goin' Back" among the set's 15 tracks.

"Goin' South," "I Came To Dance," Cry Tough" and "Code of the Road" do not lose anything in the live translations and represent the best of Nils' work since the authorized bootleg.

There are some thin spots. "Keith Don't Go" is musically sound but lyrically trite. (Actually, Lofgren may have more than the Rolling Stones' welfare in mind when he wails "Keith, don't go to Toronto." It was there that the Stones completed their own live release which presently is outselling Lofgren's by leaps and bounds.) "Beggar Day" and "Moon Tears" are reworked well, but "Like Rain" suffers a bit from a lack of vocal strength.

Overall, Lofgren's rock 'n' roll image, which wavers begween punk and power-house, improves with "Night After Night." It is not as clear a distillation of his live persona as "It Is Time . . ." is of Peter Allen's, but "Night After Night" aims for the jugular and connects more than it misses. A live record seems a fitting showcase for Lofgren's present brand of panache.