What we're talking about here vastly exceeds a mere mutual admiration society.

What Herbie Hancock, Wayne Shorter and Joni Mitchell comprise now after so much music together is a kind of musical family. So often have they appeared together on her discs over the years, that's how abundant and warm is the love that radiates from virtually every track of Herbie Hancock's celebration of Joni Mitchell "River: The Joni Letters" (Verve).

She even appears on one cut of her own tribute disc -- "The Tea Leaf Prophecy," which unfortunately, preserves a reference to "the Johnny Carson show" which dates the song needlessly but which she sings with all the weathered and smoked richness she brought to one of her late-life masterpieces, the disc of standards called "Both Sides Now."

Men have been falling in love with Joni Mitchell for almost half a century. Some do it physically, some spiritually, some musically. (Some are lucky enough to do so in all aforementioned ways, adding some the rest of us can't imagine).

But "Don Juan's Restless Daughter" will be 64 in November, Herbie Hancock is 67 and his friend from Miles Davis' legendary mid-'60s band, Wayne Shorter, is 74.

The blood may have its short heyday but not the ear, as the disc proves. The ear endures.

Hancock and Shorter's tribute to their friend Joni Mitchell is so voluptuously tender and loving that it's almost startling.

Such is the phenomenal musical warmth of this musical family that guests as high-level as Tina Turner, Norah Jones and Leonard Cohen fit in as if they too have been joining them for recording studio Thanksgivings for decades.

Turner's contribution, in fact, has got to be one of the blindfold tests of all time singing Mitchell's "Edith and the Kingpin" with Hancock and his band (which includes the incredible bassist Dave Holland and West African guitarist Lionel Loueke).

Once upon a time, an Ikebedviled Turner bragged "we never, never do nothin' nice and easy." Now that she is about to be 68, Turner can function with ear-opening sophistication as an after-hours jazz singer with some of the best jazz musicians alive.

Hancock has always been a piano impressionist out of Debussy and Ravel when he wants to be, but Joni Mitchell's songs bring about such rich, free-form reimaginings that some of her best songs flirt with unrecognizability as pronounced as Turner's voice on "Edith and the Kingpin." The lavish harmonic jewelry of the settings and freeform melodism are so hypnotic that one of the two non-Mitchell songs -- Shorter's jazz standard "Nefertiti" -- is almost as hard to recognize in its melody line as "Court and Spark" is at the outset until Jones begins to sing the words.

On the other hand, the other non-Mitchell song -- Duke Ellington's "Solitude" -- is such that even Hancock isn't going to journey all that far from the melody.

Mitchell's most famous song, "Both Sides Now," is, nevertheless, harmonically transformed and performed in such a slow-motion trance that its true melodic identity is only alluded to a couple of times in briefest passing. (In that sense, it even outdoes Art Tatum's fantasia on "Tiger Rag" in which the mind-boggling improvisation comes first and the melody at the end, as a virtual coda.)

What was once music of early wisdom and resignation is now a harmonic veil concealing a maturity that hadn't really been won yet.

By the time you get to Leonard Cohen's deep, teak-voiced recitation of her Rousseau song, "The Jungle Line," Hancock is calling attention to Mitchell the poet. This is not Ellington's "Jungle Music" here, this is a poet's dark voice accompanied only by a sensitive piano impressionist.

Of the non-A-list guests, Corinne Bailey Rae does best with Mitchell's "River." Luciana Souza's "Amelia" seems, frankly, more the product of Hancock's enthusiasm than anything else.

Obviously, the core of Hancock's "River" is the fraternal musical relationship of Hancock and Shorter that began four and a half decades ago and which Joni Mitchell cherished so much she eventually put it on as many of her discs as she could.

They are, musically, telling you how much they love their musical sister.

One of the year's truly rare discs.

*** 1/2 (Out of four)