Mikko Toivanen began his career as a musician in the early 1970s in the dance music scene in Kuopio, and soon joined the activities of the Kuopio Big Band. In the 1970s, he studied at the Jyväskylä Conservatory under the guidance of Esa Pethman and graduated with a degree in musicology from the University of Jyväskylä in 1981. During his time in Jyväskylä, he played in the Jyväskylä Big Band and even wrote arrangements for it, and led his assembled 7-member Dixieland Band.

Subsequently, for over 35 years, he held various teaching positions in music education at community colleges, music institutes in Joensuu and Kuopio, Savonia University of Applied Sciences, and the Sibelius Academy, as well as managerial and organizational roles in music education at various levels for over 25 years. For the last 15 years, he was employed at Savonia University of Applied Sciences. As part of his duties as rector, he developed jazz music education in Eastern Finland: Toivanen, for example, established these programs in Joensuu in the 1980s and in Kuopio in the 1990s. He has been an advocate and organizer of comprehensive, cross-border music education in Eastern Finland.

Mikko Toivanen has been actively involved in local and national jazz association activities and held several positions of trust in state administration in the music sector. Since the early 1970s, he has been involved in promoting live jazz performance in Jyväskylä and Joensuu in various roles as a musician, arranger, and orchestra leader. Since 1992, he has been actively involved in jazz club activities in Kuopio (JazzSavo ry, later Kuopio Jazz & Blues ry); one of the "discoverers" of the Kuopio Music Center jazz club and also one of its organizers. Toivanen was named Kuopio Jazz Musician of the Year in 1995. Toivanen has participated in various state-appointed music sector working groups (Ministry of Education and Culture) and also held national positions of trust, including eight years on the board of the Finnish Jazz Federation in the 2000s, also as vice chairman.

Mikko Toivanen is a pioneer in jazz research in Finland in the spirit of phenomenology and semiotics; his dissertation on the philosophy of jazz was completed in 2000. He was part of the writing group that published the book Savon Jatsi in 2010. In 2018, he published the first Finnish big band arrangement guide Ideat stemmoiksi, which has been described as a fundamental work in the field.

Toivanen supports traditional jazz and entertainment music, as well as new trends. Alongside jazz, he has an equal passion for classical music, for example. His own playing inspirations come from swing, west coast, and cool jazz. He has arranged music for many small ensembles and big bands, including the Kuopio City Orchestra. The classical-romantic and impressionistic styles are closest to his heart.

In addition to Toivanen's quartet, his own bands include Savonia Swing Band and Savonia-tentetti, which occasionally expands into the 12-member Savonia Big Band.