The Seattle Symphony commissioned the piece that won this year’s Pulitzer Prize for music, “Become Ocean,” by John Luther Adams. But it is a late-20th-century work that is bringing the orchestra broader fame this week: its performance with Sir Mix-A-Lot of his bawdy song “Baby Got Back,” which by Tuesday had been seen more than 1.5 million times on YouTube.

A seven-minute video of the song, opening with the lyric “I like big butts and I cannot lie,” has gone viral, stirring both admiration and dismay among other classical musicians, who have argued online about whether it was an inspired bit of fun or a tawdry gimmick.

The video even created a new star: “the lady in the black dress,” as she became known on the web. The woman was a member of the audience who joined several dozen other women on the stage with Sir Mix-A-Lot and whose enthusiastic dancing created an online sensation.

The lady in the black dress, or Shawn Bounds, as she is known in real life, said in an interview that she had “the time of her life” at the concert on Friday, and had not realized at the time that the performance would be preserved on video. “All I remember is me, Sir Mix-A-Lot, and the Seattle Symphony — as far as I was concerned, no one else was there,” she said.