Käyhkö was born in Petrograd (now St Petersburg) in 1916, while the Grand Duchy of Finland was still part of the Russian Empire, to railway conductor Juho Käyhkö and Aina née Palmros.

[2] He completed junior high school, and went on to study construction, qualifying in 1940 as a master builder (rakennusmestari), although he never practised his trade.

He was a founding member of one of the leading post-war voice ensembles, the Kipparikvartetti quartet, established in 1950, where he sang 2nd bass.

[1] One of his most popular recordings is Rakastan sinua, elämä [fi], which was certified gold in 1972, and which four decades later remained among the top 20 best-selling Finnish singles.

[1][4] Between 1940 and 1959, Käyhkö also acted in over 20 films of different genres, from musicals to comedy to crime drama.