Jack Jones with Dean Martin. With Judy Garland. With Johnny Carson. With Jimmy Durante. With Peggy Lee. With Ed Sullivan. As television images of Mr. Jones with this or that show business legend flashed on two video screens at the Oak Room of the Algonquin Hotel on Wednesday evening, the implicit message seemed to be that Mr. Jones, now snowy haired, leonine and celebrating his 50th anniversary in show business, is the last one standing. In 1962, when he had his first hit, “Lollipops and Roses,” Mr. Jones was the handsome, fresh-faced new kid on the block in an already established tradition of honey-dripping lounge lizards who swing. Today he is the same animal, but his weathered voice is filled with seams and crevices. It is the voice of a gentleman rancher astride a horse, surveying his property in a television western. It is said that as we age, we become more and more ourselves. And the mature Jack Jones has refined a style that could never be called cookie-cutter. His world-weary cragginess coincides with an impulse to take ballads at extremely slow tempos and to execute them with the hesitations, drawn-out notes and sudden leaps that are a trademark of the jazz singer Mark Murphy. Because the lower end of Mr. Jones’s voice has deepened, his sudden flights into a quasi-falsetto are more dramatic than ever. At times they suggest the spontaneous eruptions of a polished stylist impatiently throwing caution to the wind. The Beach Boys’ “God Only Knows,” the only rock song in his program, was treated as a semioperatic aria, with a Chopinesque piano accompaniment, its high drama culminating in a keening cry. “Not While I’m Around,” the ballad from “Sweeney Todd,” was turned into an earnest father-son bonding song in which the ominous tone of a father’s vow of protection suggested a gangster promising revenge, if necessary. Almost as original was a tricky Afro-Cuban version of “Just in Time.” On the up-tempo numbers Mr. Jones and his band ? Jeff Colella on piano, Chris Colangelo on bass and Kendall Kay on drums ? cut loose and swung hard. Mr. Jones has a healthy sense of humor. Reflecting on “‘The Love Boat’ Theme,” he joked that he had made of millions of dollars by threatening to sing it. Then he did. It wasn’t so bad. Jack Jones appears through Sept. 20 at the Oak Room at the Algonquin Hotel, 59 West 44th Street, Manhattan, (212) 419-9331, www.algonquinhotel.com.