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90% of this tab has been verified by Porcupine Tree's live performance of Blackest Eyes on MHz in 2003. All positions etc. should be pretty much perfect. There are detailed notes on tone etc. in the score. The only part we (DDTonFire, new_noise) are not 100% sure about is the chorus, but it's probably pretty close anyway.
Colin Edwin uses a fretless bass(as usual) with a drop D-tuning in this song, which means that the strings are tuned D-A-D-G, instead of E-A-D-G. He also improvises a lot in the verse(s) so feel free to improvise during those parts. If you choose not to; you got a pretty accurate version of the verse(s) right here, in this tab... :)
new_noise: The organ chords are not totally exact to the recording, they are arranged to be easily playable by a guitar.