We often find practices related to light and sound in yoga. You can see a lot of such elements as sexual secretion, red and white in Kaula Tantrism, as well as in the yoga of nathas and siddhas. These elements can be described both as liquid substances and as forms of light (fire). Abhinavagupta described the sounds of anahata and the manifestation of the entire matrika, as a manifestation of Shiva and Shakti passions, linking this with the theory of Shabda Brahman. However, the connection of sound with light and liquid can be traced in the Vedas, I offer quotes from the most ancient one, the Rig Veda.
Sound as light:
07.101.01 (Mandala. Sukta. Rik)
तिस्रो वाचः प्र वद ज्योतिरग्रा या एतद्दुह्रे मधुदोघमूधः ।
स वत्सं कृण्वन्गर्भमोषधीनां सद्यो जातो वृषभो रोरवीति ।।
tisro vācaḥ pra vada jyotiragrā yā etadduhre madhudoghamūdhaḥ ।
sa vatsaṃ kṛṇvangarbhamoṣadhīnāṃ sadyo jāto vṛṣabho roravīti ।।
VII, 101. To Parjanya
1. Pronounce three speeches ahead of which is the light,
(Those) that are milked from this udder flowing the honey.
Creating a calf, a plant fragment,
Barely born, the bull immediately roars loudly.
01.138.02 (Mandala. Sukta. Rik)
प्र हि त्वा पूषन्नजिरं न यामनि स्तोमेभि: कृण्व ऋणवो यथा मृध उष्ट्रो न पीपरो मृध:।
हुवे यत्वा मयोभुवं देवं सख्याय मत्र्य: ।
अस्माकमाड्गूषान्द्युम्निनस्कृधि वाजेषु द्युम्निनस्कृधि ।।
pra hi tvā pūṣannajiraṃ na yāmani stomebhiḥ
kṛṇva ṛṇavo yathā mṛdha uṣṭro na pīparo mṛdhaḥ।
huve yatvā mayobhuvaṃ devaṃ sakhyāya matryaḥ।
asmākamāḍgūṣāndyumninaskṛdhi vājeṣu dyumninaskṛdhi ।।
I, 138. To Pushan
O Pushan, after all, I urge you forward, by praising,
Like horse in a riding, that you disseminate the hostile intentions.
Like a camel (a load), pass over (through us) hostile plans!
When I call you, blessed
God, (I,) mortal, for friendship,
Make our praises brilliant,
To get awards, make (them) brilliant!
02.009.04 (Mandala. Sukta. Rik)
अग्ने यजस्व हविषा यजीयान् श्रुष्टी देष्णमभि गृणीहि राध:।
त्वं हृासि रयिपती रयीणां त्वं शुक्रस्य वचसो मनोता ।।
agne yajasva haviṣā yajīyān śruṣṭī deṣṇamabhi gṛṇīhi rādhaḥ।
tvaṃ hṛāsi rayipatī rayīṇāṃ tvaṃ śukrasya vacaso manotā ।।
II, 9. To Agni
4. O Agni, sacrifice the libation as the best sacrificer!
With (your) ability to favorably listen, accept cordially the gift (and) offering!
After all, you are the master of wealth,
You are the inventor of brilliant speech!
Sound as liquid:
09.057.01 (Mandala. Sukta. Rik)
प्र ते धारा असश्रतो दिवो न यंति वृष्टयः ।
अछा वाजश्र सहस्त्रिण ।।
pra te dhārā asaśrato divo na yaṃti vṛṣṭayaḥ।
achā vājaśra sahastriṇa ।।
1. Your flows, without drying out, are moving forward,
like raindrops from the sky,
To the thousandth reward.
09.057.02 (Mandala. Sukta. Rik)
अभि प्रियाणि काव्या विश्वा चक्षाणो अर्षति ।
हरिस्तुंजान आयुधा ।।
abhi priyāṇi kāvyā viśvā cakṣāṇo arṣati ।
haristuṃjāna āyudhā ।।
2. Looking at all the pleasant
Poetic works, flowing
Golden, shaking with weapons.
IX, 34. 6. To Soma
समैनमहुता इमा गिरौ अर्षन्ति सस्रुर्तः ।
धेनूर्वाश्रो अवीवशत् ।।
samainamahutā imā girau arṣanti sasrurtaḥ ।
dhenūrvāśro avīvaśat ।।
6. These songs, non-deflecting, one way
are flowing one way all together to him.
The roaring caused the mooing of milk cows.
A hymn to Soma
त्वं धिय मनोयुज सृ्जा वृष्टिं न तन्यतुः ।
त्वं वस्तुनि पार्थिवा दिव्या च सोम पुष्यसि ॥
tvaṃ dhiya manoyuja sṛjā vṛṣṭiṃ na tanyatuḥ ।
tvaṃ vastuni pārthivā divyā ca soma puṣyasi ॥
09.100.03 (Mandala. Sukta. Rik)
Release a poetic thought, harnessed by the spirit,
As the thunder (releases) rain!
You cause prosperity, o Soma,
Earthly and heavenly goods.