Sebastian began writing songs before entering "Australian Idol". "All I Need Is You", the second single from his debut album "Just as I Am" was written when he was a teenager, and fine-tuned during his time on "Idol". He also wrote gospel songs for his church during his teenage years. One of them, "Adore", was included in their 2004 album "Paradise Live: Adore". Sebastian wrote or co-wrote most of the songs on his albums "Beautiful Life" and "Closer to the Sun", and all the tracks on his albums "Like It Like That" and "Armageddon". In an article in "The Daily Telegraph", Kathy McCabe said of his songwriting skills, "Sebastian has matured into a genuine hitmaker, his gift with melody so finely-honed he can pretty much punch out a catchy number in his sleep." Jamie Horne wrote in "The Border Mail", "The inaugural winner's longevity [...] can be attributed to the fact that he's an accomplished musician and songwriter" and AllMusic reviewer Jon O'Brien said, "it's a testament to his vocal abilities and songwriting skills that, unlike many of his fellow winners, he's remained popular enough to see out his rather ambitious Sony contract [...] a subtle and natural progression with each album, explains why he's managed to survive once the show's publicity machine died down."