without missing a beat

次ぎのジョークにあった表現が気になりました。
A man called to make reservations on a small charter plane.
The clerk said, "The plane is very full with baggage and passengers."
Then she asked, "How much do you weigh, Sir?"
Not thinking clearly, he responded, "With or without clothes?"
"Well," said the clerk without missing a beat, "how do you intend to travel?"
"without missing a beat" は不整脈ではないとの意味もあるでしょうが、ここではもちろんそんな意味ではないはず。　
"missing a beat" で辞書を見ると、
・American Heritage Dictionary: Hesitate momentarily, out of embarrassment or confusion. This expression is most often used in a negative context, as in He sidestepped the reporter's probe into his personal life without missing a beat, or Not missing a beat, she outlined all the reasons for her decision. This expression alludes to the regular beat of musical time.
・Merriam-Webster's Online Dictionary: to deviate from regular smooth performance: the company changed ownership without missing a beat.
次ぎの辞書は "without missing a beat" の項で説明していました。
・Cambridge Idioms Dictionary: if you do or say something without missing a beat, you continue confidently with what you are saying or doing: She was asked what single achievement she was most proud of. 'My son,' she replied, without missing a beat.
音楽でテンポが一定で狂わない感じなのですね。