1. Don't go on unless you've translated the garbled announcement.
2. Don't go on until you've figured out what's going on with the glass case and switch and keyboard.
3. You are at a Vogon Poetry Appreciation Session. The Vogon Captain is about to read you his favorite poem. The Guide's entry on Vogon Poetry makes clear that this is extremely nasty.
4. Because you have already flipped the switch on the glass case and listened to the recording, you know that you'll have to listen to the second verse of the poem in order to get the atomic vector plotter.
5. This poetry is painfully awful. Have you tried STOP THE POETRY or COVER MY EARS or DON'T LISTEN TO THE VOGON POETRY?
6. 'Why not relax and enjoy it?'
7. When he finishes the first verse the Captain says, "You didn't look like you enjoyed my poetry at all!" and then proceeds to have you thrown into space.
8. You want to ENJOY THE POETRY, any time between when the Captain begins the poetry reading and when he completes the end of the first verse. If you do so, the Captain will continue on and read the second verse.
9. Now that you've heard the glass case's recording and the second verse of the poem, you know what to type on the keyboard in order to acquire the atomic vector plotter. (You'll have to wait until the guards drag you back into the Vogon Hold, of course.)