Mai was born and raised on the island of Saaremaa in Estonia. She started taking classical violin lessons at the age of 6, and piano lessons a year later. In her early teens, she started taking vocal lessons and participating in local song contests. Mai was a founding member of a popular student band, 2+2=5, led by the iconic guitar player and teacher, Tiit Paulus.

At the age of 16 she fell in love with bass guitar and since then she has dedicated her life to bass playing, both as a sideman, as well as a band leader.

After graduating high school in 2007, she moved to Tallinn to study with the legendary Estonian bassist, Raul Vaigla, whose personal influence on Leisz has been substantial. He introduced her to jazz fusion and helped shape her path.

During the years in Tallinn, she worked hard to become the bass payer she dreamed herself of becoming. Her tireless work ethic, and desire to be better than good on her instrument, led to performing with some of the biggest names on Estonian music scene, such as Tonis Magi, Riho Sibul, Lembit Saarsalu, Aces of Basses, Ain Agan, Kerli and Jaak Johanson among others.

She graduated Georg Ots Tallinn Music School in 2010 and continued her studies at Skurups Folkhogkola in Sweden.

Mai moved to Sweden in 2010 to study at Skurups Folkhogskola. In the fall of 2010, she formed a jazz-fusion band, MaiGroup, with whom she started to play her original compositions. The founding members of MaiGroup were Daniel Norden on saxophone, Ludwig Lindell on piano, Alf Carlsson on guitar and Henrik Holst Hansen on drums.

In 2011 Mai got admitted to The Royal College of Music in Stockholm where she received her bachelor (2014) and masters degrees (2017).

Since all the MaiGroup members stayed behind in Skurup, she decided to find other musicians to play with her. She connected instantly with Jonathan Lundberg on drums, Björn Arkö on saxophone, Calle Stålenbring on guitar and Rasmus Lindelöw on piano. MaiGroup recorded and released their first album Luv in 2013. When Rasmus Lindelöw quit the band to pursue his own dreams, Simon Berggren became MaiGroup’s new piano player. In October 2015 MaiGroup released their second album, You.

It took several years, a lot of hard work and endless hours of practicing her bass until Mai became a well known name on Swedish music scene (Mai Agan at the time). Eventually she was working with musicians from pop to jazz to country. She toured with pop star Linnea Henriksson, worked with jazz saxophone legend Håkan Broström, New Places Orchestra and Norrbotten Big Band. She shared the stage with pop artists such as Carola and Petra Marklund, and toured extensively with country star Doug Seegers.

In 2016 she was honored with one of the biggest jazz awards in Sweden - Alice Babs Jazz Stipendium. She was also nominated to the Jazz Cat Newcomer Award by Swedish Radio.

In December 2015 Mai recorded the first song for David Crosby’s upcoming album and became his recording and touring bassist for the next 7 years until his retirement announcement in 2022.

In 2016, she flew to Los Angeles, California and he stayed at Crosby’s house for 5 days where she spent time with his family. David and Mai wrote some songs together, including Here It’s Almost Sunset, which was released on his Sky Trails (2017) album.

Since moving to the USA, Mai has also toured with Jackson Browne, recorded with Michael McDonald, Karla Bonoff, Bill Frisell and Charles Lloyd; and performed with Kenny Loggins, Jeff Bridges, Seal, David Foster, Joan Baez, Glen Phillips among many others.

In 2019 Mai flew MaiGroup from Sweden to Los Angeles and they recorded their third studio album, Metamorphosis, at Jackson Browne’s Groove Masters Studio in Santa Monica. The album was released in the spring of 2019.

In 2020-2021 Mai released original music under her own name with a new California-based jazz-fusion group featuring Michael Landau on guitar, Greg Leisz on lap steel guitar and Gary Novak on drums.

For the last couple of years, Mai has withdrawn from the public eye, social media, touring and performing to focus on writing and recording her original music. She released her vocal debut ep What Love Can Be in 2025.