The female-fronted five-piece is getting ready to take to the stage at the Garage tonight for one of its biggest performances, after TV channel Kerrang! snapped up the band's latest video for its playlist.
Bass player Ross Archibald can't believe the unsigned group's good fortune and shares the excitement of fellow members Neil Ramsay, Amy Blair, Ana Nowosielska and Richard Passe about tonight's show.
Ross said: "The Garage is capped at 700 people capacity, but as it's our headline show we're hoping that it will sell out.
"It seems to be close already if all the support bands are accurate about how many tickets they've sold."
The support comes in the form of three local groups - South Side rock band Goldleaf, Dancing With Dakota and Life on Standby.
"They're Glasgow bands who have been on our radar for the last few months and we wanted to do something with them," said Ross.
When Altered Sky formed three years ago, its members hit it off straight away despite the fact they don't all share the same musical tastes.
This is something 24-year-old Ross thinks helps them to be more creative.
He said: "The music I like is a bit different to what we write and play.
"Our music is rock music, but it's a radio friendly, American college, pop-rock sound. "I'm a big Dream Theatre fan and I like prog and prog-metal, but everyone else is really different so it's strange that it works.
"The only person who likes music similar to what we actually play is Amy, the drummer, who is a fan of Yellow Card and Lost Prophets.
"I think it does help us to be more creative with things as we have different musical tastes; we all have different inputs and ideas and it all comes together.
"There's no real falling out or arguments while writing music; we all come from different styles but there's no major difference of opinion - it's all very smooth."
Back in 2010, they would never have imagined such success but their dreams are slowly coming true after the video for new single, Where I Belong, was debuted on the website of rock music channel Kerrang!.
After the debut, the TV channel snapped up the video, as did rival station Scuzz, and it will soon be shown on their daytime playlists.
The rock band also received their first play on American radio stations last week, which Ross described as "totally surreal".
He said: "I've been playing bass since I was 14 and I've always been playing music, but I never imagined I'd be playing the main stage at the Garage, or be on Kerrang! or anything like that so it's crazy."
"When I was 14 to 15 years old, Kerrang! was all I watched and I used to imagine what it would be like to appear on it and how good it would be.
"Now that we're there, I don't really know what to think."
Last Saturday saw the band perform an acoustic set at an ice hockey match before an audience of more than 2000 sports fans at the Braehead Clan's home ground in Glasgow.
Organisers were so impressed they signed up Altered Sky to perform at four more games throughout the season.
"We got to watch the game, sell merchandise and advertise ourselves to all these people," said Ross.
"The reception was really good."
As well as warming up the crowd before matches, the group is planning a new European tour which will start in March, and a month-long tour of America.
They also hope to visit schools while in the States, and take musical master classes with the kids, telling them what it's like being in a band, going on tour and making music.
Tickets for the show, costing £8, are available from www.alteredsky.com