His father was forced to stop teaching music during the Nazi period, and died in mysterious circumstances on 18 August 1943.

[4][6] Hans' early life was one of extreme poverty, with no running water at home, surviving on vegetables grown in the garden, and having to walk several kilometres to school daily.

[4][7] In late 1958, Jaki moved to Cologne and enrolled at the Hochschule für Musik und Tanz Köln, encouraged by his friend Manfred Schoof.

They shared a flat for the next three years, playing together as a loose collective of "Jazz Cookers" with multi-instrumentalist Gunter Hampel, saxophonist Olaf Kübler (who would later manage the krautrock group Amon Düül II), Lothar Meid (future bassist with Amon Düül II).

[10] In 1963, Jaki was offered a gig as full-time drummer at the Jamboree club in Barcelona, performing there for the next seven months with pianist Tete Montoliu.

At that time, the Jamboree harbored the touring musician from the United States, and Jaki had an opportunity to play shows with Chet Baker and Don Cherry.

[4] Schoof put together a quintet in 1965 featuring Jaki on drums, Buschi Niebergall on bass, saxophonist Gerd Dudek, and pianist Alexander von Schlippenbach.

[12] Schoof had a connection with composer Irmin Schmidt, who asked Schoof's quintet in 1966 to perform on Schmidt's soundtrack project for West German film Zwei wie wir – und die Eltern wissen von nichts [de].

The quintet also took part in a recording of "Die Befristeten" composed by Bernd Alois Zimmermann, which came out on a Wergo label in 1967 and accompanied "Ode to Freedom in the Form of a Dance of Death", a radio production of a play by Elias Canetti.

In late 1967, Jaki was searching for new opportunities, and when Irmin Schmidt asked for a drummer recommendation, decided to sign up himself.

Jaki surprised Schmidt, when he turned up at the band's rehearsal himself and played a drum beat with a routine inspired by the world music, removed from free jazz.

Cyclopean was a project that involved, other than Jaki, Irmin Schmidt from Can alongside long time collaborators Jono Podmore (Kumo / Metamono) and musician and producer Burnt Friedman.

[26] With Can: With Holger Czukay: With Irmin Schmidt: With Alex Wiska [de]: With Michael Rother: With Phantom Band With Joachim Witt: With Phew: With Eurythmics: With Gianna Nannini: With Damo Suzuki Band: With Jah Wobble: With Pluramon: With Club Off Chaos: With Burnt Friedman: With Robert Coyne: With others: