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 electro-acoustic folk and pop music, rap and urban sound art together.
In 2019-2021 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.
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 and Kaustinen, Finland.