The Story Behind The First Ever Mixer

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The Story Behind The First Ever Mixer

The mixer, an integral bit of kit in any DJs set-up yet not much is widely known about the invention that literally plays the most important role in any DJs lives.

After spotting an image online last week purporting to be the first mixer ever my curiosity grew as to how such a humble invention was spawned.

rosie alex rosner

An early prototype but not the first, this version even included a switchable cue. 


The age old question, the egg or the chicken right? In this case it was beat-matching that was first recognised by Francis Grasso who is thought to be the ‘Godfather of DJing’ sometime around the 1960’s who initially counted the tempo with a metronome that helped him look for and play similar records.

From there he needed something better to mix his records which is where Alex Rosner’s work began on a simple red box dubbed ‘Rosie’ that was installed in the Haven Club where Francis was a resident.

Alex Rosner was no stranger to the clubbing scene having installed a technically sound system for his famed ‘The Loft’ after-hours parties so it made sense he’d play a role in the first baby steps of the mixer.


Turns out ‘Rosie’ wasn’t built from scratch but was a modified mono mixer from Bozak who still make high quality equipment today.

Originally it was made for broadcast but with permission from owner and creator Louis Bozak, Alex was able to customise it using two headphone amplifiers for the cueing system and a sliding fader and even set about testing the ruggedness of it.

So I took a bottle of Coca Cola and I poured it on the mixer. That was my reliability test, I thought that was a realistic test, little knowing that DJs probably don’t drink Coca Cola’s. But I felt that Coca Cola was corrosive because I knew when I put it on my car battery, it dissolves the corrosion at the battery terminal. So I felt that had some effect. When I poured the Coca Cola in the mixer fader it had no effect. So I got back to Bozak and I said: “You got it, that’s it, it’s reliable!” Then the CMA 10-2 was born, that was a standard of the industry.”

The rest is history with Alex Rosner pioneering the mixer all the way back in 1965 and that has led to globally recognised companies such as Pioneer, RANE and Traktor.



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