Jaap Spek (1929–2001) was a sound engineer and philosopher associated with the WDR Studios in Cologne, where he worked with Stockhausen, among other notable experimentalists.
At the Westdeutscher Rundfunk, Spek was involved in developing and teaching technologies for the recording and performance of music by contemporary experimental composers. Stockhausen wrote in the liner notes of Microphony I regarding Spek’s contribution:
"… One day I took some equipment from the WDR Studio for Electronic Music home with me. My collaborator Jaap Spek helped me… During this, Jaap Spek changed the filter settings and dynamic levels, improvising. At the same time, we recorded the result on tape… The tape recording of this first microphony experiment constitutes for me a discovery of utmost importance. We had not prearranged anything; I used several of the laid-out implements at my own discretion while probing the tam-tam surface with the microphone, as a doctor auscultates a body with his stethoscope. Spek reacted - spontaneously as well - to what he heard as the result of our joint activity… Actually, this moment was the genesis of a live electronic music with unconventional music instruments.”