The Hybrid Theory EP (also known simply as The EP) was the demo CD recorded by the band Linkin Park back when their name was Hybrid Theory. (See Linkin Park for details of the change) It consisted of six songs, plus an untitled secret instrumental track (which is linked to the last track, after approximately 6 minutes of static). Only one thousand copies were produced, and those thousand CDs are now in very great demand within the Linkin Park fanbase. In 2001, Linkin Park started a fanclub called the LP Underground, and those who joined in the first year received a reprinted copy of the EP. The reprint, while not as rare as the original run of a thousand, is still quite rare and again is in great demand.

There are some subtle differences between the original and the re-release, most notably, the original inside cover had a quote on the picture, the re-issue does not. (The quote is "After eight months, she was sure of one thing: that the baby's future would be determined by the convergence of its divided past." It is unknown as to what it means, though some have suggested that it refers to the band's divided hip hop/hard rock style.) As well, the original inside booklet had general credits and what appears to be an X-ray picture of the baby on the cover, while the re-release has small pictures of the band and a letter to the fans, along with credits.

The band occasionally plays the EP's songs at live shows. High Voltage was remixed as "H! VLTG3" by Evidence, Pharoahe Monch and DJ Babu and put on 2002's Reanimation album. What appears to be a version of the untitled secret track appears on 2003's Meteora as track 12, Session. However, while similar, they are not the same song, nor are they different versions of the same song. This idea can be disproven by Meteora's liner notes for Session: "Mike created...this song...in the back of the bus...it felt unfinished for over a year." The gap between Hybrid Theory's EP and Meteora is far more than year, or even two.

Track listing

1. "Carousel" - 3:00
2. "Technique" (short) - 0:39
3. "Step Up" - 3:54
4. "And One" - 4:30
5. "High Voltage" - 3:30
6. "Part of Me" - 3:50
7. (Untitled) - 2:40

Total time (excluding static between "Part of Me" and "Untitled"): 22:03. Including the static, the CD is 28:19 in length.

Note: The album cover is *not* in fact an X-RAY picture of a baby - this kind of technology is not yet around. Ultrasounds are the only things that can 'view' a baby in a womb. (With the exception of one or two new technologies currently being developed).

In fact, if you watch the Linkin Park: Frat Party at the Pankake Festival then you'll see that Mike Shinoda is talking about the 'creative minds' in LP, and shows the painting like so:

Personnel

• Chester Bennington - vocals, writing
• Mike Shinoda - emcee, vocals, writing, production, mixing, art direction, cover art
• Joe Hahn - DJ, samples, writing, cover art
• Rob Bourdon - drums, writing
• Brad Delson - guitar, writing
• Phoenix Farrel - bass, guitar, cello
• Kyle Christner - bass
• Pat Kraus - mastering
• Mudrock - production, mixing