The men who sing 1,500 songs all over the world in seamless harmony

Question: What does the music of J. S. Bach, the Beatles, Cole Porter, Monteverdi, Stephen Foster, Tchaikovsky, and Randy Newman have in common? Answer: Nothing. Except it's all likely to show up on a program of the King's Singers.

In case you've missed one of the 2,000 concerts given from England to the Far East since this highly acclaimed British ensemble left King's College, Cambridge, back in 1968, your time has come.

A six-part television series, videotaped on location in five European countries, begins this Thursday (July 25, 8 p.m. Eastern standard time, Arts and Entertainment Cable Network; check local listings). Entitled The King's Singers' Madrigal History Tour, the series will help explode the notion that the popular songs of the Renaissance are any less accessible musically than those of our own day. Called ``the most satisfying form of music ever devised for recreational singing,'' madrigals might surprise m any viewers with how often they strike a universal note in the themes they cover -- from lost love to housework to the pangs of earning a living.

With the songs sung perhaps as expertly as can be by one of the form's most successful exponents, program selections will trace madrigal styles from the Italian frottola and Spanish villancico of the late 15th century to the sophisticated contrapuntal style of the English madrigalists of the early 17th century.

Lest that sound like too-heavy going, the King's Singers have developed an enormous following by the sheer panache of their performing and the almost mystical blend of their a cappella voices.

``They're sensitive, mature, and have all the technique to transcend the music itself,'' says Harrison Powley, professor of music at Brigham Young University, who earned a PhD in Renaissance music from the Eastman School of Music.

``They make the music fun for all ages, all tastes -- even though it's old, perhaps in a foreign language -- because they project the spirit that's in between the notes. And they understand the musical style of the day like few groups do,'' Professor Powley explains.

Madrigals and sacred Renaissance music are not all the King's Singers are about, however. One of their goals has been to broaden audience understanding of music through the ages by mixing the old with the new.

``We want to provide a wide entertainment over a range of difficult material that's as interesting to people as possible,'' says Alastair Hume, one of the group's countertenors. That could be the understatement of the decade, perhaps, as the group's 1,500-song repertoire has earned them the label ``world's most versatile musical singing group'' from dozens of critics.

In performance, or on 22 available records, you'll find such diversity as Hoagy Carmichael's ``Lazy River,'' the Beatles' ``Ob-La-Di Ob-La-Da,'' both genteel and bawdy madrigals, and sacred Renaissance liturgical chants. Constantly seeking new material, they have commissioned works from such top modern composers as Peter Maxwell Davies and Ned Rorem.

Regardless of the song, the unaccompanied voices -- two countertenors, one tenor, two baritones, and a bass -- are a wonder to hear.

``We try to make the sound of a warm, male voice ensemble -- that is to say, blended to sound like a single instrument,'' says countertenor Hume. ``Right from the very bottom of the bass to the top of the highest countertenor, it all sounds like the same register.''

The group says most people these days are not used to listening to unaccompanied voices. ``But because most people believe they have a voice, or at least pretend they are Tony Bennett in the bathtub, they find themselves identifying more with what we are trying to do,'' says the group's newest member, Colin Mason. ``They find they love the pure voices without all the complications of acoustic, orchestral, or rock accompaniment.''

It all began in 1965, when six of the choral scholars at King's College, Cambridge -- students with special scholarships to study music and sing in the university's famous choir -- felt they sounded good enough to tour local schools. The idea burgeoned until they formally grouped as ``the King's Singers'' in 1968. Members have changed over the years, although three of the originals remain.

Now each of the six earns a full living on yearly tours to the United States, Europe, Australia, New Zealand, and beyond. On recent tours in America, they were featured on both NBC's ``Today'' show and Johnny Carson's ``Tonight.''

Wherever they go, they emphasize that the overall blend comes from painstaking attention to voice production and sublimating individual egotism to the concerns of the whole.

``We all have quite small voices, really,'' Mr. Mason says. ``None of us alone could be heard on the stage of the Met opera house. But when it all clicks in, it can be so enchanting -- it caught on five hundred years ago and has been going strong ever since.''