A shift in how the popular puppet is deployed marks the most visible change on ''Sesame Street,'' the children's program that began its 43rd season on public television on Monday.

The ''Elmo's World'' segment is being phased out after 13 years, replaced by a new segment, ''Elmo the Musical.'' Ten new skits, each lasting 11 minutes, have been prepared.

The idea is to incorporate music into the ''Sesame Street'' emphasis on introducing concepts in science, technology, engineering and math to the preschool-aged viewers, said Rosemarie Truglio, senior vice president of education and research at Sesame Workshop, the company that makes the series.

Elmo will use singing and dancing to draw attention to the need for problem-solving skills and make the learning entertaining, she said. The character will be featured in ''Sea Captain the Musical,'' ''Mountain Climber the Musical'' and ''President the Musical.''

The current Elmo, geared largely to 2-year-olds, had some repetitive music segments. ''Elmo the Musical'' will have seven or eight songs in each skit, and will be aimed at preschool youngsters who are slightly older.

''With really young children, the arts are very relevant to their lives,'' Truglio said. ''We want to be able to use the arts as a tool.''  ''Sesame Street'' began its emphasis on science and technology last season.

The children's show is also bringing in its usual series of guest celebrities this season: Charlize Theron, Halle Berry, Melissa McCarthy, Steve Carell, John Hamm, Zac Effron, Blake Griffin, the rock band Train and rapper Common.