Well, if you start at exactly 27:11 (that is after this strang "sin"
sound) then she says exactly {ngI' chu' muD}.
Maybe that was the speaker's error, because like on the tapes Okrand
says "ng as in thing, or hang", so the speaker might have had "thing" in
her mind, and forgot to drop it while speaking the line.
Qov has told the story of what happened, but I can't recall where. IIRC, the speaker was unable to pronounce initial {ng}, so they decided to have her say "sing" and have the sound editor cut it off, except that instruction was miscommunicated so the recording was cut off at the wrong end. Or something like that.
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De'vID