In the ancient and Jewish churches, 'songs' were prophesies about the Lord, especially His coming in the world, subjugation of evil spirits, and liberation of the faithful from their assaults. 'Heavenly songs' are voiced affections or affections expressed and modified by sounds. As thoughts are expressed by conversation, so affections are expressed by songs. From the balance and flow of the variations, angels perceive the object of the affection.

(Referenties: Conjugial Love 55)

195. The most ancient people did not compare all things in man to beasts and birds but actually called them such. This was their manner of speaking, which also remained throughout in the Ancient Church after the Flood; and a similar manner of speaking was preserved among the Prophets. Man's sensory powers they called serpents, for just as serpents are next to the ground so do the sensory powers come next to the body. Consequently reasonings based on sensory evidence concerning mysteries of faith they called serpent-poisons, and those who reasoned in that way they called serpents. And it is their basing reasonings so much on sensory evidence - that is, on visual, as is the evidence of earthly, bodily, worldly, and natural objects - that is the reason for the statement 'the serpent was subtle, more than every wild animal of the field'.

[2] A similar usage occurs in David,

They make their tongue sharp, like a serpent. Under their lips is the poison of an asp. Psalms 140:3-5.

This refers to people who mislead a person by means of reasonings. In the same author,

They go astray even from the womb, in uttering what is untrue; their poison is like serpent's poison; they are like the poisonous deaf-adder which stops up its ear to the sound of those whispering [to it], of the wise one who belongs to the fraternity [of charmers]. Psalms 58:3-5.

Reasonings whose nature is such that those who resort to them do not even hear that which is wise, that is, do not hear 'the sound of the wise one', are here called 'serpent's poison'. This was the origin of the popular saying with the ancients about 'the serpent stopping its ear'. In Amos,

As if someone went into the house and leaned with his hand against the wall, and a serpent bit him. Is not the day of Jehovah darkness and not light, and thick darkness, and no brightness in it? Amos 5:19-20.

'His hand against the wall' stands for power that is one's own and trust in sensory evidence, which results in the benightedness described here.

[3] In Jeremiah,

The sound of Egypt will go forth like a serpent, for [her enemies] will go forth in force, and they will come to her with axes, like woodcutters. Let them cut down her forest, says Jehovah, for it will not be explored; they are more numerous than locusts, they are without number. The daughter of Egypt has been put to shame; she will be given into the hand of a people from the north. Jeremiah 46:20, 22-24.

'Egypt' stands for reasoning about Divine matters that is based on sensory evidence and factual knowledge. Reasonings are called 'the sound of a serpent', and the benightedness that results is meant by 'a people from the north'. In Job,

He will suck the poison of asps, the tongue of a viper will kill him; he will not see the brooks, the streams flowing with honey and butter. Job 20:16-17.

'Streams of honey and butter' are spiritual and celestial things, which reasoners will not see. Reasonings are called 'the poison of asps and 'the tongue of a viper'. For more concerning the serpent, see at verses 14-15, below.