Explain how Iago manipulates Roderigo in Act 2: Scene 1.

In Act 2, scene 1, Iago's comment that Othello and Desdemona "are well tuned" is a metaphor of harmonic music in which he uses to indicate the current harmony of Othello's marriage. However the comment is then followed by Iago's vow "to set down the pegs", which show his intentions to disrupt the harmony between them. When Iago and Roderigo are left alone together, Iago sees this as an opportunity to manipulate Roderigo by telling him that "…showed first 75 words of 986 total…

…showed last 75 words of 986 total…paranoid as he suspects that Othello has slept with his wife Emilia. However, it seems as if he could just be using that as an excuse to ruin the harmony between Othello and Desdemona as he insulted Emilia earlier on. It seems that Iago doesn't care about the after affects of what will happen when his plan fully succeeds, but only of his own intentions, which strongly suggest that he is a very gluttonous person.