In "Promenade," Mussorgsky uses many common melodies that have slight variations between them while setting them in the "call and answer" style between the instruments of the orchestra. In the very beginning, you will hear the main theme stated by the solo trumpet, which is then echoed by the entire brass family. This pattern is repeated three times between the trumpet solo and brass family in their eleven beat phrases (rhythm sections A and B).
The second main section is then taken over by the strings in the orchestra as they play the next variation on the theme with the woodwinds echoing them each time the strings play. Then the two families quickly switch roles as the woodwinds take over the melody with the strings adding soft echoes to their theme.
Finally, as the piece comes to an end you will again hear all the voices playing different parts until you once again hear the brass family play the main theme which is echoed by the entire orchestra to the end the piece.

Now, before you go back to listen to the piece and for these melodies and instruments remember........
 
               - listen for the instruments which have the melody and which
                    instruments have the echoes
               - listen for how many different sections you can hear with each
                    variation of the main theme

Go and listen.......