So you're hearing Bsus4b9 with that CMaj7 shell, no problemo. Dark sound, which is Jordan's point in a way - how a Maj7 voicing can be made to sound dark, or I should say, how one can reveal the darkness in a Maj7. Try this one - play a minor triad from the 3rd of C (Emin). Now you have a CMaj7 chord made to sound like an Emin chord. The 5 and 1 of Emin are the Maj7 and 3 of CMaj7. Turns out that Maj7 note reveals a dark quality as in the two examples above. If you play a GMaj triad over CMaj7 you'll notice that the Maj7 tone is gone, replaced by a 9 = CMaj9. Bright, cheery. Same with C6, bright, cheery. CMaj7? Dark. It's interesting to note that you heard that B as the dominating tone - shows that your ear was hearing "dark". Exactly!