I'm fairly certain this is Middle American Pronounciation. I'm from Pennsylvania, and we always say 'sikth'. I'm an exchange student right now, though, and I've met a Long Islander, Canadian, and a girl from Florida. They all properly say 'sixth', and seem suprised that I don't. Even now trying the proper way is difficult for me, and I can't say it without thinking first. So I would say people from the Midwest and Plains states have a rather simplified pronounciation of object number six.
SikTh ended in 2008.
SikTh was created in 2001.
A few of the song titles by the band Sikth include Scent of the Obscene, Peep Show, and Skies of Millennium night. The band originate from Watford, Hertfordshire, UK.
song - Seal Jubilee Guitar, Vibraphone - Natasha KhanKeyboards - David KostenVocals [Sea Sounds] - Mikee Goodman