In this lockdown (dread phrase!, as Wallace Arnold almost certainly would have written), we have been encouraged to stride warrior-like over intellectual mountains. Reach for The Iliad or Paradise Lost, say the clever ones. It’ll improve you. Conquer the operas of Wagner, or the quartets of Beethoven. Learn a language. Build a boat. Or maybe pour yourself a glass of something pleasing, and soak in the comforting tub of that most enriching of entertainments, the Great American Songbook.

There’s nothing wrong with stretching the mind. As Lorenz Hart’s lyric in Pal Joey reminds us: “I was reading Schopenhauer last night — and I think that Schopenhauer was right.” The gloomy philosopher who changed Wagner’s life also brought out the best in Hart, who was related, wouldn’t you know, to Heinrich Heine. And we start with Hart because he was the first, and he was the best.

Well, not the first. Not quite. Jerome Kern and Irving Berlin put down significant markers in the second decade of the twentieth century; Kern with music, Berlin with words as well. But it was the collaboration of Hart and Richard Rodgers which changed everything. One hundred years ago, in the summer of 1920, they collaborated on their first show, Poor Little Ritz Girl, and watched as the balloon went up. Kern and Oscar Hammerstein may have constructed Showboat, the hit of 1927, but that much-thumbed Songbook bears the prints of those alumni of Columbia, so different in temperament, who formed an ideal pairing.

“Dick Rodgers simply pees melody,” said Noel Coward, and those partnerships with Hart and Hammerstein put him in a class of his own. With Hammerstein, who had greasepaint in his blood, he wrote the super soaraways that lit up Oklahoma!, Carousel, South Pacific, The King and I, and The Sound of Music. But it was Hart, the wilful alcoholic homosexual dwarf, who prompted him to write the songs that made him immortal. Those bitter-sweet songs, loved by singers and jazzers alike, that seem to improve with the years: “My Funny Valentine”, “Little Girl Blue”, “I Wish I Were In Love Again”, “I Didn’t Know What Time It Was”, “The Lady is a Tramp”.

Hart’s astringent lyrics, set against the sweetness of his partner’s melodic gift, represent the high-water mark of song as popular entertainment. The Gershwins and Cole Porter saw their own ships rise in the water, and the flotilla was augmented by Frank Loesser, Harold Arlen, Jule Styne and a dozen others. The admiral of the fleet was Rodgers, on the bridge at all times, even if he wondered where his pal Larry had got to.

What is the supreme performance of a Rodgers and Hart classic? Tony Bennett, on the second of his superb recordings with Bill Evans in the mid-Seventies, presented “You’re Nearer” in the manner of a lieder singer. Sinatra’s version of “Spring Is Here” catches the greatest interpreter of the Songbook in midsummer form. Hear the yearning in that drawn-out “spring” when the line comes round a final time! The personal vote, however, goes to Ella Fitzgerald’s reading of “It Never Entered My Mind”.

Ella’s Rodgers and Hart Songbook was the second in that famous sequence of long players supervised by Norman Grantz for Verve, the record label he founded in 1956 to supply the stage he felt she needed. Porter’s songs had supplied material for the first LP, a record that is not quite as good as folk memory suggests. There were some wonderful performances, of course, and “Ev’ry Time We Say Goodbye” became the singer’s calling card. But she skates over some songs, and isn’t up to the particular challenge of others. “You’re the Top”, for instance, goes for nothing.

Listen to her singing “I Concentrate on You”. Then cock an ear to Lena Horne, who gives the song a fire that was beyond Ella’s emotional range. It’s the difference between a millpond and a Roman candle. People tend to overlook La Horne these days. They shouldn’t.

Dick and Larry’s songs brought out other qualities in Ella, heard most clearly in “It Never Entered My Mind”. Hart surpassed himself in this lyric, from the opening words of the introductory verse (“I don’t care if there’s powder on my nose”) to the repetition of the title with which he bids us the most melancholy of farewells. This recording, arranged by Nelson Riddle, is incomparable. A great singer is paying tribute to the greatest song (possibly) by the greatest pair of songwriters (unarguably) in the English language. It should be in the Smithsonian.

Where are the other performances to accompany Ella and Horne? Peggy Lee’s version of “Then I’ll Be Tired Of You”, by Arthur Schwartz and Yip Harburg, is jolly good. The lady may have been mad as a cut snake but the bruised romanticism, the hope that things might just turn out for the better, made her unique. Johnny Hartman, another voice we don’t hear often enough, covered Berlin’s “Falling in Love is Wonderful” in 1963 with John Coltrane, and it works beautifully. Even Coltrane, such a terrible honker when he thought no one was looking, behaved himself.

I also have a soft spot for Perry Como’s tender recording of “It Could Happen To You”, by Jimmy Van Heusen and Johnny Burke: “Keep an eye on spring, run when church bells ring … ” Nor can I forget walking into Michael’s Pub one evening in autumn and hearing Maureen McGovern opening her set with “Long Ago and Far Away”, one of Kern’s key-shifting classics adorned by Ira Gershwin’s shimmering lyric.

Then there is Fred Astaire, the man who introduced so many songs by Berlin, Kern and Gershwin. “If I want to know whether one of our songs works,” Gershwin said, “I only have to hear Fred sing it.” There was no performing practice when Astaire cast his peepers over those tunes. He was forging the way ahead alone, and his performances will never pall. “I’m Old Fashioned”, written by Kern and Johnny Mercer, brings out the wit and grace we associate with this incomparable entertainer. Porter’s “Dream Dancing” isn’t far behind. You can’t go wrong with Astaire. He scattered stardust on everything he touched.

For all Bing Crosby’s artistry — he altered the preferred vocal range from tenor to baritone — the identity of the greatest performer is not in doubt. “The voice of a lifetime,” Crosby himself said of Frank Sinatra. “My lifetime.” It wasn’t only the voice. It was the ears. Sinatra learned so much from Harry James and Tommy Dorsey that when he stepped out of the band, and got through the bobby-soxer years, he was equipped to become the singer he wanted to be.

“The Capitol years”, we call them, when Sinatra found his “cello” voice, and, supported by the finest arrangers, wrote his own imperishable chapters in the tale of that Songbook. It began in 1955 with “In The Wee Small Hours”, Riddle by his side. Then came the most spectacular hat-trick in popular music: Only The Lonely (1958), No One Cares (1959) and Nice’n’Easy (1960). This is the unassailable Sinatra, who could do no wrong. Some of these performances — “You Go To My Head”, “Guess I’ll Hang My Tears Out To Dry”, “A Cottage For Sale” — are, to use a much-abused word, definitive. Others have sung these songs, often very well, but they belong to Frank.

Can we find one cut that speaks fully for this supreme artist? We can. The song, written by Van Heusen and Burke, appears on No One Cares, though it is the arrangement by Gordon Jenkins that carries “Here’s That Rainy Day” into the stratosphere. That, and Sinatra’s complete mastery of a mournful song that, in his hands, becomes the most lyrical three and a half minutes in popular music.

Now for the best of Ella and Bennett, Sinatra’s comrades in the mighty triumvirate. From Ella we shall take “Midnight Sun”, a song composed by Sonny Burke and Lionel Hampton, to which Johnny Mercer supplied the words after he had heard it on his car radio. This is Mercer at his most playful, as he rhymes “red and ruby chalice” with “alabaster palace” and then “aurora borealis”. The worlds of jazz and popular song mesh cleanly here, and the outcome is sheer joy. It may be 99 to 100 but I love Mercer above even Hart. He is the most American of the great American songwriters.

Which leaves Bennett, who is still with us at the age of 94. What riches he has left us, and nothing is richer than that first record with Evans, recorded in 1975, when pianist and singer speak as one voice. Once again Van Heusen and Burke take the honours, this time with “But Beautiful”, one of the pillars of that great Songbook which has given more pleasure to more people than almost anything.

Of course, there’s also much to be said for The Iliad. But be warned: it doesn’t end well. Achilles should really have stayed in his tent.