"999,999" is the first track from the Nine Inch Nails album The Slip. The song's title and instrumental nature may suggest a reference to the Ghosts I–IV, and the transition with the song "1,000,000" into the new style of The Slip.
The accompanying artwork seems to be made of six '9's, three of which are facing down, with their tails merging with the tails of the '9's facing upward. The three facing upward '9's could also be in fact '6's, that could very well tie this first track with the last, "Demon Seed." The artwork for the sticker from the CD/DVD release is the same as the digital release, but with the red lines omitted.
This is the original album version. Consisting solely of synthesizers and a manipulated sample of Reznor's voice, it builds slowly in volume and layering until cutting out and leaving Reznor's voice to transition into "1,000,000." In this way, its structure is similar to "Pinion."
This song is used as the introduction song on 2008's Lights In The Sky Tour.
While the song is an instrumental, a short vocal can be heard at the end:
How did I slip into (this)?