Hi Bastian,
During my PhD I used the "APE Perceptual Evaluation toolbox" that I obtained from the following link/repository
https://code.soundsoftware.ac.uk/projects/ape. I used the toolbox initially for pairwise comparisons but later I adapted it for running "triadic comparisons"... If the toolbox is at the same stage when I downloaded it, you may need to do some update in the code related to figure handles for newer versions of MATLAB.
The same research group developed later a very reliable web-based version of the same toolbox (for me required only Google Chrome and Python being installed), web audio evaluation toolbox (WAET) available at
http://www.semanticaudio.co.uk/projects/waet/
I hope this can be useful for you, see you!
Alejandro
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Alejandro Osses V., Ph.D.