回答
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I haven't seen him on TV lately, but I see he's continued playing music.
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I haven't seen him on TV in a long time, but I see he's still a musician.
「音楽活動」を直訳すると「music activities」になりますが、あまりそういう表現は英語で聞いた事ないです。「playing music」や「being a musician」の方がいいと思います。