As Dirgesinger is a lot like a bard collecting lore of songs, uses musical powers I would hope they would be given non cursed bard songs. They would still retain the lowered ability to use the bard songs, but it would provide benefits for this class especially for those who do not summon undead.
My reason for this is any class can take this as a subclass with the two-feat dip (Iron will and skill focus perform) several classes also gain a benefit from this class (Warlock's can gain curse song with a merit and now Harbinger can as well). It also has a synergy with assassins all of which may not wish to add a bard dip.
The closest example of why this would not be overpowered is the Cleric Evangelist. The free path cost nothing and gains a feat, where the above classes still require two feats.
