Well known and respected throughout Scandinavia, Michelsen was admired as principal horn of the Danish State Radio Symphony Orchestra, and as a soloist, chamber musician, and distinguished teacher.

Michelsen was one of the most loved chamber musicians in Denmark. His outstanding technique and flexibility over the whole range of the instrument, combined with his brilliant musicianship endeared him to many.

David Sternbach noted that Michelsen inspired respect with "formidable technique, a uniquely beautiful tone quality" and that Michelsen played with a "grace and ease that had to be seen to be appreciated."

He also developed his own "D" descant horn and mouthpiece designs, and was a skilled furniture maker.