Hello.
Warlocks can change their curse songs/bard songs with Eldritch Euphony synergy feat.
The feat Harbingers have, Herald of the Grave, does not let them do the same.
Right now, when you type -song to change active songs, you get this prompt.
My suggestion is simply: Allow curse song switching with harbinger's Herald of the Grave feat, like it is with Warlock's equivalent. It is thematic, and cool to be able to choose which curse song you use especially as Harbinger.