With each song arranged to last three to four minutes, after singing the first song on a good note, the customer had to insert another coin while he was singing the second song, and therefore he spent a lot of 100-yen coins without thinking... which became a typical pattern.
1曲は3～4分になるように調整されており、1曲目を気分よく歌ったあと、2曲目の途中で次のコインを投入する必要が出てくるため、客はついつい100円玉を景気よく使ってしまう……というパターンが生まれた。