Also, would it be possible to create heretical charm that would allow to disregard EB' Witness to Darkness Charisma penalty to Oramus music charms? Or would it be imbalanced?
I will, as usual, just recommend that people use the fan-errata for WtD that @Jon Chung and I devised years ago.
Article: Witness to Darkness: Replace paragraph beginning with "Finally...", with "Finally, the Infernal is unimpressed with the murk of others' guile, and adds her Essence rating to her MDVs against inherently deceptive social attacks and as bonus successes to recognize or pierce another's deceptions. Her attunement to lies makes it harder to be honest, however, imposing a -Essence internal penalty to all attempts to be honest and straightforward, save when truth brings more pain than lies." In addition, as with Hateful Wretched Noise, the penalty imposed by bright light can be ignored for a scene with the expenditure of 1 Willpower.
Hence, you can play strangely alluring music using Charisma just fine - just remember to have some subtlety in your lyrics, so just don't try to seduce someone while singing "Love me, love me, say that you love me".