@whale-av thanks for the info, I just found something ( https://github.com/mgsx-dev/pd-offline ) that seems to work, so I'll use that

So how can I for apply an effect like e.g. freeverb~ on a file but without playback,basically manipulating the audio as fast as possible(essentially post-processing) and generate a new file? Is this possible? I can only use effects like delay,reverb,flanger etc live currently.