Heini Mielonen is a singer, cellist, composer, and lyricist. She has studied music at institutions such as the Royal Danish Academy of Music, Malmö Academy of Music, the Sibelius Academy, and Metropolia University of Applied Sciences. Mielonen actively performs both as a jazz singer and a cellist, seamlessly blending these two instruments in her music. In 2024, Mielonen released her debut album Step Forward! under the Eclipse record label, receiving a warm reception.

As a pioneer of her instrument, Mielonen has tirelessly expanded the cello's possibilities, exploring its sonic landscapes and introducing it into musical contexts where it is not traditionally heard, such as jazz. Mielonen's original compositions incorporate elements ranging from symphonic and electro-acoustic music to the passionate cha-cha-cha rhythms of artistic Latin music. Her music moves between ethereal, melancholic cello looping soundscapes and hypnotic, groove-infused jazz tones. Her compositions can be described as an adventurous journey through classical music, jazz, and ambient soundscapes—yet they resist confinement to any single genre.

Mielonen leads her own jazz ensemble, the Heini Mielonen Quintet. She has performed extensively both in Finland and internationally, both with her own groups and as a soloist—both as a singer and a cellist. She is currently working on her second album.