Born Peter Paul Cetera on September 13, 1944, in Chicago, Illinois, Cetera grew up on the city's South Side as one of six children in a Polish-American family. Music wasn't originally centered around the bass guitar that would eventually become inseparable from his image. His parents bought him an accordion when he was young, and Cetera proved sufficiently talented to win a local accordion competition. There are many roads into rock and roll. Starting with an accordion and eventually becoming the voice behind “25 or 6 to 4” is one of the less heavily traveled ones.

As a teenager, Cetera became increasingly interested in rock and roll. He bought an acoustic guitar, later switched to electric bass, and began performing with local groups. One of his important early bands was The Exceptions, a popular Chicago-area group that released recordings and performed extensively around the Midwest. Cetera was therefore already an experienced working musician before joining the band that would make him internationally famous.

That band was originally called The Big Thing, an ambitious Chicago group formed around musicians including keyboardist Robert Lamm, guitarist Terry Kath, drummer Danny Seraphine, trombonist James Pankow, trumpeter Lee Loughnane and saxophonist Walter Parazaider. Their unusual lineup combined a conventional rock rhythm section with a full horn section, giving them a sound that was immediately different from most late-1960s rock bands. Cetera saw the group performing at a club and was impressed. He joined in late 1967, replacing bassist Bob Amato.

The group moved to Los Angeles, signed with Columbia Records and adopted the name Chicago Transit Authority. Their self-titled debut album appeared in 1969, an adventurous double LP combining rock, jazz, soul, psychedelia and extended instrumental passages. After the actual Chicago Transit Authority objected to the band's name, the musicians wisely concluded that fighting a metropolitan transportation agency probably wasn't essential to musical success and shortened the name to simply Chicago.

Cetera's bass playing was an important part of the early Chicago sound. His instrument had to operate underneath an unusually busy arrangement containing guitar, keyboards and three horn players, and he developed a melodic approach that did more than simply mark the root notes. Yet it was his voice that increasingly brought him to the front. Cetera's high tenor contrasted beautifully with Robert Lamm and Terry Kath, giving Chicago several distinctly different lead vocalists.

One of the earliest demonstrations came with “25 or 6 to 4,” written by Robert Lamm and released in 1970. Cetera sang lead over Terry Kath's ferocious guitar work and the band's charging horn arrangement. The song became one of Chicago's signature recordings and remains one of the clearest examples of the group's original formula: sophisticated musicianship combined with enough rock power to prevent anybody from mistaking the horn section for the local marching band.

Cetera also began developing as a songwriter. His composition “Where Do We Go from Here?” appeared on Chicago II, while later albums increasingly featured his writing. His contributions included “What Else Can I Say,” “Happy Man” and other songs that demonstrated the melodic instincts that would eventually become central to both Chicago's later music and his solo career.

Then came “If You Leave Me Now.”

Written and sung by Cetera, the ballad appeared on Chicago X in 1976. It represented a considerably softer side of a band that had built its reputation on ambitious horn arrangements and muscular rock performances, but audiences embraced it enthusiastically. “If You Leave Me Now” reached No. 1 on the Billboard Hot 100 and became Chicago's first American chart-topping single. It was also a major international hit.

The song brought Chicago Grammy success, winning Best Pop Vocal Performance by a Duo, Group or Chorus. It also established Cetera as one of rock's most recognizable ballad singers. His voice had an unusual combination of range and vulnerability: he could push upward into notes that sounded emotionally strained without actually losing control of them. It was ideal for songs about relationships hovering approximately three seconds away from catastrophe.

Chicago continued through a period of profound change. Guitarist Terry Kath died accidentally in 1978, a devastating loss personally and musically. The band continued, but its sound gradually evolved. By the early 1980s, Chicago had experienced declining commercial fortunes and a change of record label before beginning one of popular music's more impressive career revivals.

Producer David Foster became a major part of that revival with Chicago 16 in 1982. The album placed greater emphasis on polished contemporary pop production, keyboards and power ballads. Cetera's voice moved increasingly to the center of the band's commercial identity.

The defining song was “Hard to Say I'm Sorry.”

Written by Cetera and Foster, it became a huge success, reaching No. 1 on the Billboard Hot 100 in 1982. The song introduced Chicago to a new generation of listeners and helped transform the band from a veteran act associated with the 1960s and 1970s into a major force on 1980s pop radio. The horn section was still there, but the musical landscape surrounding it had changed dramatically.

Chicago 17 followed in 1984 and became the band's biggest-selling studio album. Cetera was everywhere. He sang lead on “Stay the Night,” “Hard Habit to Break,” “You're the Inspiration” and “Along Comes a Woman,” while co-writing several of the album's major songs. “You're the Inspiration,” written with David Foster, became another enduring romantic standard and one of the songs most closely associated with Cetera's voice.

By this point, however, the enormous success of Chicago had created a difficult question about Cetera's future. He wanted greater freedom to pursue solo work while remaining associated with the band, an arrangement that proved difficult to reconcile with Chicago's touring and recording commitments. In 1985, after approximately 17 years with the group, Peter Cetera left Chicago.

He had actually released his first solo album, Peter Cetera, in 1981 while still a member of the band, but it had achieved limited commercial success. His post-Chicago solo career was about to proceed rather differently.

In 1986, Cetera released Solitude/Solitaire. Its first major single was “Glory of Love,” written by Cetera, David Foster and Diane Nini for The Karate Kid Part II. The song became an enormous hit, reaching No. 1 on the Billboard Hot 100 and earning nominations for both the Academy Award and Golden Globe for Best Original Song.

“Glory of Love” gave Cetera something particularly important: a No. 1 hit entirely outside Chicago. Any question about whether audiences had been buying Chicago records for the band rather than recognizing Cetera individually was answered rather decisively.

It also became permanently attached to The Karate Kid universe, providing the emotional soundtrack for Daniel LaRusso and Mr. Miyagi's journey to Okinawa. Apparently crane kicks, ancient rivalries and teenage romance require a man capable of singing extremely high notes.

Cetera wasn't finished with the charts. Later in 1986 he teamed with singer Amy Grant for “The Next Time I Fall,” another No. 1 Billboard hit. The duet gave Cetera consecutive chart-toppers from the same album and confirmed that leaving one of America's most successful bands hadn't exactly sent his career into hiding.

His 1988 album One More Story produced “One Good Woman,” while Cetera also recorded another memorable duet, “After All,” with Cher for the 1989 film Chances Are. The song became a major adult-contemporary hit and further established Cetera as one of the era's most dependable duet partners. If a movie needed two attractive people to realize they were hopelessly in love while the credits approached, somebody apparently checked whether Peter Cetera was available.

His later solo recordings included albums such as World Falling Down, One Clear Voice, You're the Inspiration: A Collection and Another Perfect World. Although the enormous chart dominance of his mid-1980s period eventually subsided, Cetera continued touring and performing for many years, drawing upon both his solo catalog and songs associated with his years in Chicago.

One aspect of Cetera's musicianship can occasionally become overshadowed by the ballads: he is an excellent bass player. Early Chicago recordings make that particularly clear. Cetera developed melodic bass lines while simultaneously singing demanding lead vocals, a combination requiring considerable independence between voice and hands. The elaborate arrangements of early Chicago weren't built around musicians merely standing in the background keeping time; every instrumental part could become remarkably busy.

His distinctive vocal sound was also influenced by an unusual incident early in his career. Cetera has recounted being attacked at a baseball game after refusing to stop talking, suffering a broken jaw that had to be wired shut. He has said that singing through the wired jaw influenced the way he learned to sing with less jaw movement. It is surely one of the stranger methods of vocal development in popular music and is not recommended as a substitute for professional lessons.

Chicago's importance was formally recognized in 2016 when the band was inducted into the Rock & Roll Hall of Fame. Cetera was included as a member of the inducted lineup, recognizing his central contribution to the group's classic recordings. He did not attend the induction ceremony after discussions about performing with his former bandmates failed to produce an agreement.

The absence disappointed fans who had hoped for a reunion, but it did little to diminish Cetera's place in Chicago's history. His voice appears on many of the band's most recognizable recordings, and his songwriting became particularly important during the period when Chicago successfully reinvented itself for the 1980s.

Cetera eventually withdrew from regular touring. In interviews surrounding his later career, he made clear that he was increasingly content away from the relentless demands of traveling and performing. After decades of concerts, recording sessions, airports, hotels and being expected to reproduce “Glory of Love” at full altitude night after night, deciding that staying home might be pleasant hardly requires an extensive psychological explanation.

His legacy occupies an interesting position because it effectively contains two substantial careers. The first belongs to the long-haired bassist standing amid Chicago's horn section, singing rock songs while the band experimented with jazz, progressive arrangements and sprawling double albums. The second belongs to the polished solo performer whose soaring ballads became fixtures of 1980s radio, movie soundtracks, weddings and romantic mixtapes.

They sound like very different worlds.

Peter Cetera's voice connects them.

There is something remarkable about an artist who can be immediately identified on recordings separated by decades and musical styles. Put on “25 or 6 to 4,” “If You Leave Me Now,” “Hard to Say I'm Sorry,” “You're the Inspiration” or “Glory of Love,” and within moments there is no uncertainty about who is singing.

The hairstyles changed. The production changed. Chicago changed. Popular music changed.

That voice didn't.

And somewhere, somebody is still hearing the opening notes of “Glory of Love” and immediately preparing to defend Mr. Miyagi's honor.