Dr. Dischord and the DYNNE are quite the dynamic duo. Here's the low down on these guys: they live near the Valley of Sound, and their behavior contributed to the Soundkeeper's decision to lock all the sounds away.
The DYNNE is like an orphan genie – yep, he's made of smoke! – that the doctor has adopted. Except the DYNNE can't really grant any wishes: he can only create awful and disturbing sounds. But even though he seems like a trouble maker, the DYNNE just genuinely loves terrible noises. And after all, he does end up doing some good deeds, like when he brings some of the escaped sounds back to the Soundkeeper.
The doctor, too, isn't all bad. Even though he's a bit of a grump, he has done a long-term good deed by adopting the DYNNE. And at least he's honest about the fact that he's not a very good doctor: "I only treat illnesses that don't exist: that way, if I can't cure them, there's no harm done – just one of the precautions of the trade" (11.56-57). The doctor tries to give Milo, Tock, and the Humbug some medicine that will cure their noise problems (which, by the way, they don't have), but he isn't so evil that he forces the medicine on them when they refuse. When they continue on their journey, he's happy to stay in his little house, plotting bigger and better noises to unleash upon the world.