Haapoja's musical background is in the new wave folk music. However, Haapoja has graduated from the Centre for Music & Technology, Sibelius Academy, and studied music with wide perspective from classical and jazz theory to contemporary music composing. In 2013 Haapoja founded the alternative hiphop collective haapoja & illmari. The collective combines electroacoustic folk and pop music, rap and urban sound art together.
In 2019-2022 Haapoja is creating his first solo album for the project called Unheard Landscapes, where Haapoja's global field recrodings meet electronic new wave folk music. Haapoja's main instrument is jouhikko, the Finnish bowed lyre.
Haapoja's artistic work is a mixture of music & soundscape composing and video art. Helsingin reitit – The Routes of Helsinki is Haapoja's long term art project, which focuses on soundscapes in the boundaries between nature and the city. Haapoja's sound art piece Luotisuora - Beeline is a part of the permanent exhibition in the new Helsinki City Museum. In November 2016 the piece was installed first time in Manhattan, New York. In September 2019, all The Routes of Helsinki works were exhibited at the Sound Art Gallery Akusmata, Helsinki. Finnish national broadcasting company YLE premiered the 2010-2020 soundscape collage of The Routes of Helsinki in May 2020.
In 2021, various Haapoja's new soundscape works were presented around Finland: in EMMA Espoo Museum of Modern Art, Retretti Punkaharju Art Cave and Tytyri Lohja, in Kalevan Navetta, Seinäjoki and furthermore at Helsinki City Museum's inner yards alongside the museum's permanent exhibition.
Keitaat / Oases, created with Amanda Kauranne, is a series of audio-visual installations about Nordic nature. With the piece Oases from HEL (2017) Haapoja & Kauranne have toured in North Iceland, New York and Helsinki. In 2022, Keitaat / Oases project will continue in The Faroe Islands and is going to be performed in Berlin, Germany and Kaustinen, Finland.