The two melodies are rising and falling. Speakers use pitch to send various messages. I am amazed. I was sure I put it there. Intonation is used to put certain words in the foreground.
Speakers use pitch to give words stress.
Low pitch is used to put things in the background, to treat something as old, to show anger, or as shared information. Intonation is used to signal ends and beginnings in conversation. It is used to show whether a situation is open or closed. A high or rising pitch indicates an open situation, whereas a falling pitch indicates a closed situation. Intonation is used to show expectations.