Getting back to the topic of this thread, it is noteworthy that occult music, unacceptable dancing, and unacceptable singing all characterize the use of rock music and rock-based music, including in much of CCM and CWM.
In that regard, Scripture speaks of occult whispering of occultists who engage in occult practices with demons:
Isaiah 29:4 And thou shalt be brought down, and shalt speak out of the ground, and thy speech shall be low out of the dust, and thy voice shall be, as of one that hath a familiar spirit, out of the ground, and thy speech shall whisper out of the dust.
God here reveals to us that those who have familiar spirits (demons) speak "out of the ground" and their speech whispers "out of the dust."
Previously, we have seen that God commands that His people sing out loud. In connection to that revelation, we see also that He speaks of the evil practice of occultists who use whispered speech.
His revealing this evil practice of occultists instructs us that our speech and therefore also our singing must not be conformed to any extent to the wickedness of those with familiar spirits.
Whispered singing has zero place in acceptable corporate worship. Consecrated believers must reject and denounce all such singing in churches.