Lee Jordan is the fellow prankster of Fred and George (in canon). "Lee Jordan" had sounded like a Muggleborn name to me, implying that he would be capable of instructing Fred and George on a tune that Harry would know. This was not as obvious to some readers as it was to your author.
Draco went to Slytherin, and Harry breathed a small sigh of relief. It had
They were approaching the Ps now...
And over at the Gryffindor table, there was a whispered conversation.
And Minerva McGonagall, from where she stood at the speaker's podium of the Head Table, looked down at the next name on her list.
"Potter, Harry!"
There was a sudden silence in the hall as all whispered conversation stopped.
A silence broken by a horrible buzzing noise that modulated and changed in hideous mockery of musical melody.
Minerva's head jerked around, shocked, and identified the buzzing noise as coming from the Gryffindor direction, where They were
Dumbledore was chuckling.
Minerva's eyes went back to Harry Potter, who had only just started to step out of line before he'd stumbled and halted.
Then the young boy began to walk again, moving his legs in odd sweeping motions, and waving his arms back and forth and snapping his fingers, in synchrony with Their music.
"HARRY POTTER!" shouted Lee Jordan, and the Weasley twins performed a triumphant chorus.
"HARRY POTTER!" There were a lot more voices shouting it this time.
The Weasley Horrors went off into an extended wailing, now accompanied by some of the older Muggleborns, who had produced their own tiny devices, Transfigured out of the school silverware no doubt. As their music reached its anticlimax, Harry Potter shouted:
There was cheering then, especially from the Gryffindor table, and more students produced their own antimusical instruments. The hideous buzzings redoubled in volume and built to another awful crescendo:
Minerva glanced to both sides of the Head Table, afraid to look but with all too good a notion of what she would see.
Trelawney frantically fanning herself, Flitwick looking on with curiosity, Hagrid clapping along to the music, Sprout looking severe, and Quirrell gazing at the boy with sardonic amusement. Directly to her left, Dumbledore humming along; and directly to her right, Snape gripping his empty wine goblet, white-knuckled, so hard that the thick silver was slowly deforming.
Minerva's lips set in a white line. She would have words with Them about that last verse, if They thought she was powerless because it was the first day of school and Gryffindor had no points to take away. If They didn't care about detentions then she would find something else.