Folk music, which, I refer to in its contemporary form as “singer-songwriter pop,” on the surface seems an unlikely bedfellow for jazz. Folk songs use rudimentary, static chords; jazz employs advanced, active harmonies that emphasize the higher intervals. Folkies sing in an even, droning monotone; the Great American Songbook, however, is better served by singers like Tony Bennett to Ray Charles, who take full advantage of loud-soft dynamics.

Yet there is a long tradition of pop stars attempting to sing standards, from Rod “Bless the Child” Stewart on. And there have been many more successful attempts at blending jazz and folk traditions made by the late Nina Simone and some of her current day followers: Cassandra Wilson, Dianne Reeves, Lizz Wright. Now two more jazz singers, Diana Krall and Karrin Allyson – both young, blonde Grammy nominees – have taken the plunge into the singer-songwriter repertoire. Both have new albums, and both are in town this week.

Ms. Krall, who is appearing at Radio City tonight, is represented by “The Girl in the Other Room” (Verve B0001826). Last fall, she turned 40 and got married, for the first time, to the British singer-songwriter Elvis Costello. This year both halves of the marriage have new releases. Mr. Costello’s “North” release sounded jazzier than usual, while Ms. Krall’s new record is very singer-songwritery.

Six of the 12 tunes are originals by Ms. Krall or Mr. Costello. The others are primarily by major figures of singer songwriter pop: Tom Waits (“Temptation”), Joni Mitchell (“Black Crow”), Bonnie Raitt (“Love Me Like a Man”). (I, for one, am not disappointed that there is nothing from the father of the movement, Bob Dylan.)

The disc starts with “Stop This World,” by Mose Allison, who might be described as a jazz pianist who became a pop songwriter, since his tunes are rarely done by jazz people. Ms. Krall also does a fine job with her ball-and-chain’s “Almost Blue,” which has proven to be the most suitable of all of Mr. Costello’s songs from a jazz perspective (Chet Baker sang it in the movie “Let’s Get Lost”).

Ms. Krall sometimes seemed a bit reserved and cool when singing standards, but she warmed up more on recent albums like “The Look of Love” and especially “Live in Paris.” Her voice works very well with this type of quasi-folk and modern-folk material, although the mood, in both her own pieces and those of the other singer-songwriters, is dark and melancholy.

When addressing this contemporary material, both Ms. Krall and Ms. Allyson avoid trying to “jazz it up.” That is, to reharmonize the songs with jazz chords the way most jazz pianists do when they play pop songs. The major exception on the Krall album is a lengthy quote from Count Basie’s “Splanky” inserted into “Love Me Like a Man,” which is already based on the blues.

For the most part, the originals here are fine. The album most comes alive, for me, however, on the disc’s one standard, “I’m Pulling Through,” a song written for Billie Holiday by two friends of hers, Irene Kitchings and Arthur Herzog. Kitchings and Herzog are hardly George and Ira. But theirs is the strongest melody here, and the one that best suits Ms. Krall’s voice and piano. It’s got to be more than a coincidence that it’s also the most upbeat and optimistic tune in the program.

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Karrin Allyson, who begins a two-week run at Le Jazz Au Bar tonight, may look young. But I would guess from her stack of albums that she, like Ms. Krall and myself, has passed the 40 mark. If she hasn’t, she has absolutely no excuse for reliving the songs of my youth.

The difference between us, it seems, is that I grew up hating Cat Stevens and Elton John, and escaped into my father’s Duke Ellington and Bix Beiderbecke collection to get away from what everybody else my age was listening to. Ms. Allyson apparently liked the 1970s singer-songwriters – Ms. Mitchell, Mr. Stevens, James Taylor, Melissa Manchester, Carole King, Carly Simon – enough to return to them on her new album “Wild For You” (Concord CCD2220).

Every time I have seen Ms. Allyson perform in recent years (including an outstanding concert at Carnegie Hall’s Zankel Hall, where she had it all over a well-known Brazilian diva), she has grown more impressive. Her two previous albums, “Ballads: Remembering

John Coltrane” and “In Blue,” were outstanding examples of ways to make the familiar jazz songbook sound fresh and exciting.

“Wild For You,” though, sounds better on the first hearing than it does after subsequent listens. Ms. Allyson and her musical director, the very gifted Goldstein, attempted to be too faithful to the sources. Overall, the tone here is a kind of jazz-pop lite. Mr. Goldstein could have easily improved these songs (there – I said it), as he did the show tunes on Janis Siegel’s fine new “Sketches of Broadway.”

In general, I wish Ms. Allyson and Mr. Goldstein had shown enough respect for the material to disrespect it. It would have made sense to rework some of these songs a bit more: to re-imagine some of them as uptempo 4/4 swingers, or into 3/4 time, or as bossa novas – in other words, to bring different kinds of swinging rhythm to the material. Unless you’re willing to take the same chances with James Taylor that you are with Rodgers and Hammerstein, it’s just not going to work as jazz.

Here Cat Steven’s “Wild World” provoked Mr. Goldstein to include a piano solo, and Joni Mitchell’s “Help Me” does receive a touch of Ms. Allyson’s trademark scatting. But nothing sounds better coming out of her throat than Jimmy Webb’s “The Moon Is a Harsh Mistress” – mostly because it’s a great song for her to begin with.