People who are good at singing sing proudly, but they look complacent to those around them.
People who are good singers sing proudly, but it just looks like self-satisfaction to others around them.
「ひとりよがり」は英語で「complacency」または「self-satisfaction」と言います。
「Complacency」は名詞で、「complacent」が形容詞の形です。
「得意気に」は「proudly」と言います。
People who are good at singing sing proudly, but they look complacent to those around them.
歌がうまい人は得意気に歌うが、周りにいる人にひとりよがりに見える。
People who are good singers sing proudly, but it just looks like self-satisfaction to others around them.
歌がうまい人は得意気に歌うが、周りにいる人にひとりよがりにしか見えない。