Subject-verb agreement is frequently misused in broadcast and in print. Band falls into the same category as jury, family, club. They are group nouns , so singular for purposes of SAT. However, you can have a proper noun that is plural -- The Seahawks were in town last night. You can always get around your issue by saying the members of Black Sabbath were...
William K.
asked 05/14/21Of “was” and “were.”
While I’m no grammar aficionado, I rarely use Wikipedia as a source for anything, and questionable grammar is one reason of many.
Would you please tell me which is correct?
”Stillwater was a band...”
”Black Sabbath were a band...”
These examples were taken from each band’s respective Wikipedia page.
5 Answers By Expert Tutors

Jon S. answered 05/14/21
Patient and Knowledgeable Math and English Tutor
If the band sounds like a singular then use was. If it sounds like a plural use were. Example. Coldplay sounds like a singular so use was. Beatles sounds like a plural so use were. So for your example, Stillwater was a band is correct and Black Sabbath were a band is not.
Hello,
"Was" and "were" are past tense of the verb "is".
Although most sentences follow conventional noun-verb agreement, sentences with subjects such as band names and sport teams can be more difficult to determine.
Patrick S. answered 06/27/21
Experienced Yale graduate who tutors AP, ACT, SAT, SSAT, and Writing
This one shows the contrast between American and British usage. In the U.S. we say that a crowd is loving the game; in England, announces say that the crowd are loving the game. There is one band, but there are several people in the band--thus, both usages are acceptable, but if you are writing according to British conventions, you should use them consistently.

Rene K. answered 05/14/21
ESOL Teacher with 25 Years of Experience
It's important to note that this depends on whether you're talking about American English or British English. In American English, collective nouns are singular. In British English, collective nouns can be either singular or plural; they are more commonly used as plural.
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