Identifying the relative highness and lowness of pitch is something that all children should learn. Some students may perceive pitch more accurately than others, and are deemed delayed because of a misunderstanding. Since pitch is a measure of the speed of a frequency over a period of time, some students might recognize pitches as moving faster than others. Rather than saying high or low, try saying faster or slower notes instead. Another method you can use is to assign high pitches a specific color like red, and lower pitches a color like blue. Play two pitches and ask the students to identify which pitch is red and which one is blue.
Rhythm can be difficult to teach, but once the student feels it, he usually understands. The first step is to play a song and physically put the child's hands together on the beat. Then, when the child gets the hang of it, the second step is to play the song again and clap with her on the beat, without physically helping her. Finally, the third step is to play the song a third time and see if the child can do it herself. If any one of these approaches fails, return to the previous step and try again. Reinforce how well the child is doing with every repetition.
Singing is something that most children can accomplish with a little guidance. Select simple songs that move by step and don't contain any leaps or skips. "Mary Had a Little Lamb" is a good choice. Children who are developmentally delayed may have trouble singing specific pitches. If he has trouble singing the nursery rhyme, allow the child to create a song of his own and sing it for you. This will reinforce his self esteem, get him to think creatively and still develop crucial music skills.
Children that are developmentally delayed may not yet have the reasoning capabilities to listen to and discuss a song. Rather than forcing them to use words, allow them to express themselves in other ways. This can be through drawing an image about the feelings invoked by a song, or through selecting items in the classroom that she feels represent the mood. For instance, she may hear a dark and brooding song and select the largest item in the classroom as a representative object. There is no right or wrong selection with this activity, but she should have a reason for her selection. Discuss the reason for the selection of the object with her.