Primarily British spelling of 'concertize'; to arrange or present as a concert, or to perform in concerts.
From 'concert' plus the verb-forming suffix '-ise' (British spelling), which differs from the American '-ize' suffix but carries the same meaning.
The '-ise' vs '-ize' distinction in words like 'concertise' and 'concertize' is a fascinating reminder of how American and British English diverged—both are correct in their respective varieties, but they look quite different!
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