I am not sure why you thought rolling your own was a good idea, as they are now broken.
I am running latest patchlevel of Arch Linux.
The pitch slider controls the volume, and volumne and speed do absolutely nothing.
Just make this easier on everyone and just use normal slider controls:
$ pacman -Q qpicospeaker-git
qpicospeaker-git r60.7429077-1
$ pacman -Q qt5-base
qt5-base 5.14.1-4
$ pacman -Q qt5-multimedia
qt5-multimedia 5.14.1-1