This will happen in the Jungle Jazz Bar. After you talk to Harold & Barry, the singer on the podium starts to sing. Wait for the singer to start the song again. There will be a really long piano solo before she starts to sing again (around 3-4 minutes after she starts) and pull the lever next to you afterwards.
Be sure to make a save before talking to Harold & Barry as there is another achievement:
you can get here and you cannot combine it with this.