The third act begins with a very brief dialogue with a clown (rustic) and musician. This dialogue is provided for the purpose of comic relief. The play is becoming quite serious and intense, and comic relief is necessary to relax the audience. The humor of the scene relies on puns. The clown asks the musician about his “wind instruments”: (1) this literally refers to musical instruments like the oboe or flute. But (2) the expression also is jokingly used to refer to flatulence (or farting). One’s own bottom or rear end is then said to be a wind instrument. The words tale and tail are also used to add to the pun: the word tail here suggesting again the rear end or bottom of an individual. The clown is thus suggesting that the music being played is like the sound of farting.
In the second half of the scene, the main plot continues to develop. Cassio asks Iago for his wife’s assistance. Emilia is serving Desdemona, and Cassio wants Emilia to ask Desdemona if he can speak to her. Emilia, who does not know about her husband’s evil plot, is happy to help Cassio.
The extremely brief second scene serves a necessary plot function: to get Othello out of the main city so that Cassio can have the opportunity to go and talk to Desdemona. Othello, then, is going to another part of Cyprus to see about making certain that the island is secure.