How does the author develop the characters in this short story excerpt?

physical description, behavior, insight into the character's thought processes through dialogue or narration, and insight through the opinions of other characters in a story.

Explanation:

If a characters dialogue is timid then you know this character is a shy person, if the character has bright hair and a different style than most you know the character is bold (physical description), if the character often thinks rude things towards other people they are probably mean, and etc

"the tune the he might never know again." this part build anticipation. dexter got extremely happy by the piano tune. he could see what he was living at that moment in his life throught this feeling. the reader might want to learn more about his happy life. in fact, he called it a state of   'ecstasy'. the fact that he had got in a mood of intense appreciation and that everything about him was extremely bright and glamorous might lead the reader to feel that this state of happiness may not last long. the two parts from the excerpt that exemplify the anticipation are: " the sound of the "; " it was a know again."