linguistic:paraphrasing, structural:reformatting
1976–1979: Technical Ecstasy, Never Say Die!, and Osbourne's departure

Black Sabbath began work for their next album at Criteria Studios in Miami, Florida, in June 1976. To expand their sound, the band added keyboard player Gerald Woodroffe, who also had appeared to a lesser extent on Sabotage. During the recording of Technical Ecstasy, Osbourne admits that he began losing interest in Black Sabbath and began to consider the possibility of working with other musicians. Recording of Technical Ecstasy was difficult; by the time the album was completed, Osbourne was admitted to Stafford County Asylum in Britain. It was released on 25 September 1976 to mixed reviews, and – for the first time – later music critics gave the album less favourable retrospective reviews; two decades after its release, AllMusic gave the album two stars, and noted that the band was "unravelling at an alarming rate". The album featured less of the doomy, ominous sound of previous efforts, and incorporated more synthesisers and uptempo rock songs. Technical Ecstasy failed to reach the top 50 in the U.S. and was the band's second consecutive release not to achieve Platinum status, although it was later certified Gold in 1997. The album included " Dirty Women ", which remains a live staple, as well as Ward's first lead vocal on the song "It's Alright". Touring in support of Technical Ecstasy began in November 1976, with openers Boston and Ted Nugent in the U.S., and completed in Europe with AC/DC in April 1977.

In late 1977, while in rehearsal for their next album and just days before the band was set to enter the studio, Osbourne abruptly quit the band. Iommi called vocalist Dave Walker, a longtime friend of the band who had previously been a member of Fleetwood Mac and Savoy Brown, and informed him that Osbourne had left the band. Walker, who was at that time fronting a band called Mistress, flew to Birmingham from California in late 1977 to write material and rehearse with Black Sabbath. On 8 January 1978, Walker made his only live performance with Black Sabbath, on vocals, when they played an early version of the song "Junior's Eyes" on the BBC Television programme Look! Hear! Walker later recalled that, while in Birmingham, he had bumped into Osbourne in a pub and came to the conclusion that Osbourne was not fully committed to leaving Black Sabbath. "The last Sabbath albums were just very depressing for me", Osbourne said. "I was doing it for the sake of what we could get out of the record company, just to get fat on beer and put a record out." Walker has said that he wrote a lot of lyrics during his brief time in the band, but none of them were ever used. If any recordings of this version of the band other than the Look! Hear! footage still exist, Walker says that he is not aware of them.

Osbourne initially set out to form a solo project featuring former Dirty Tricks members John Frazer-Binnie, Terry Horbury and Andy Bierne. As the new band were in rehearsals in January 1978, Osbourne had a change of heart and rejoined Black Sabbath. "Three days before we were due to go into the studio, Ozzy wanted to come back to the band", Iommi explained. "He wouldn't sing any of the stuff we'd written with the other guy (Walker), so it made it very difficult. We went into the studio with basically no songs. We'd write in the morning so we could rehearse and record at night. It was so difficult, like a conveyor belt, because you couldn't get time to reflect on stuff. 'Is this right? Is this working properly?' It was very difficult for me to come up with the ideas and putting them together that quick".

The band spent five months at Sounds Interchange Studios in Toronto, Ontario, Canada, writing and recording what would become Never Say Die!. "It took quite a long time", Iommi said. "We were getting really drugged out, doing a lot of dope. We'd go down to the sessions, and have to pack up because we were too stoned, we'd have to stop. Nobody could get anything right, we were all over the place, everybody's playing a different thing. We'd go back and sleep it off, and try again the next day". The album was released in September 1978, reaching number 12 in the United Kingdom and number 69 in the U.S. Press response was unfavourable and did not improve over time, with Eduardo Rivadavia of AllMusic stating two decades after its release that the album's "unfocused songs perfectly reflected the band's tense personnel problems and drug abuse". The album featured the singles " Never Say Die " and " Hard Road ", both of which cracked the top 40 in the United Kingdom. The band also made their second appearance on the BBC's Top of the Pops, performing "Never Say Die". It took nearly 20 years for the album to be certified Gold in the U.S.

Touring in support of Never Say Die! began in May 1978 with openers Van Halen. Reviewers called Black Sabbath's performance "tired and uninspired", a stark contrast to the "youthful" performance of Van Halen, who were touring the world for the first time. The band filmed a performance at the Hammersmith Odeon in June 1978, which was later released on DVD as Never Say Die. The final show of the tour – and Osbourne's last appearance with the band until later reunions – was in Albuquerque, New Mexico, on 11 December.

Following the tour, Black Sabbath returned to Los Angeles and again rented a house in Bel Air, where they spent nearly a year working on new material for the next album. The entire band were abusing both alcohol and other drugs, but Iommi says Osbourne "was on a totally different level altogether". The band would come up with new song ideas, but Osbourne showed little interest and would refuse to sing them. Pressure from the record label and frustrations with Osbourne's lack of input coming to a head, Iommi made the decision to fire Osbourne in 1979. Iommi believed the only options available were to fire Osbourne or break the band up completely. "At that time, Ozzy had come to an end", Iommi said. "We were all doing a lot of drugs, a lot of coke, a lot of everything, and Ozzy was getting drunk so much at the time. We were supposed to be rehearsing and nothing was happening. It was like, 'Rehearse today? No, we'll do it tomorrow.' It really got so bad that we didn't do anything. It just fizzled out". Ward, who was close with Osbourne, was chosen by Iommi to break the news to the singer on 27 April 1979. "I hope I was professional, I might not have been, actually. When I'm drunk I am horrible, I am horrid", Ward said. "Alcohol was definitely one of the most damaging things to Black Sabbath. We were destined to destroy each other. The band were toxic, very toxic".