The electronics inside each box are connected to an 8m lamp cord attached to the inside of the box. The cord has a regular switch and connects to a 12V motorcycle battery. Resonators are made to reinforce sound but are also able to change the quality of a tone.
At a certain point, self-oscillation occurs. 

Hökarängen, Stockholm 2021

You can find recordings from the guerrilla actions here: https://solandersson.bandcamp.com/album/guerrilla-action-2

Vanadislunden, Stockholm 2020

You can find recordings from the guerrilla actions here: https://solandersson.bandcamp.com/album/guerrilla-action-1

Self resonating box: test 1

Self resonating box 2: test 1 & 2