It will be the talented 18-year-old's first gig since her 'Bangerz for Bushfires' relief concert earlier in the year.

"It's just a chance to connect with people again. I've missed performing live and it's a chance to do that as well," Ms St John said.

She will perform a mix of classic songs and current hits, as well as some never before heard original music.

"I've kind of taken a bit of inspiration from the virus and all the emotions that come along with it," she said.

"I've been writing everyday and playing my guitar and coming up with little original songs that I'll be performing tomorrow."

Her new songs, she said, draw on the loneliness and isolation of the coronavirus pandemic and its lockdown.

Ms St John will on Sunday be "chatting a little bit about" the original music she's been writing and producing in Sydney.

She describes her sound as "kind of contemporary pop ... alternative folk-y music", inspired by her love of musical theatre and artists such as Missy Higgins and Harry Styles.

Almost a year ago, Ms St John was one of 500 who auditioned for the chance to take part in a nationwide talent development program based in Sydney.

She was one of just eight to be selected and is about to graduate with this year's class.

As part of the program Ms St John has been working with Sydney producer Phil Anquetil, who has worked with artists such as One Direction, Little Mix and Jessie J.

"We've been doing zoom calls and online emails and stuff but basically they kind of link you up with people in the industry and tour you and then develop you as an artist," Ms St John said.

Ms St John played in front of about 300 people at the bushfire relief concert, which raised more than $2000 for recovery efforts.

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In her earlier high school years, however, she was "a bit scared to pursue music".

"I thought people would think it wasn't cool. I always kind of hid it from people. Then the last two years I got involved with the school production and fell in love with it again," she said.

"Since the [talent development] program I've really embraced it again. The last two years of highschool were a turning point in my life."

Ms St John said her family members were her greatest source of support, and her biggest fans.

"So for them to see me taking it seriously and putting in all this work it's pretty exciting," she said.

"They've supported me so much ... I owe them all a lot."

Sunday's gig will be Ms St John's first solo concert.

The performance will be streamed live on Facebook, Instagram and TikTok from 6pm.

Details can be on the concert's Facebook page.