i'm reading rhythm of war right now and navani and raboniel just successfully mixed stormlight and voidlight together with music, and oh man do i have theories
[edit: i numbered different points for better readability]
so currently i know of five types of lights-
stormlight, which responds to honor's tone
lifelight, which respond's to cultivation's tone
voidlight, which respond's to odium's tone
towerlight, which responds to the harmony of honor and cultivation's tones
and this new warlight(? i don't know the name yet) which responds to the harmony of honor and odium's tones.
even with just three base tones, there should be seven tones including a mixture of voidlight and lifelight and a mixture of all three.
the lights also apparently need rhythms to mix and interact with their surroundings, like how stormlight needs a specific rhythm to grow plants. and there are a lot of rhythms. so do all of the rhythms correspond to a different type of light?
also: singers who have bonded with voidspren hear different rhythms, or rather slightly more powerful and chaotic versions of old rhythms. so maybe that's because the normal or old rhythms were based on honor's tone, and these new rhythms are based on odium's tone. (kind of like how songs are on specific scales, like g minor or c major)
2. maybe the types of light act like colours? in the colour wheel, primary colours mix together to form secondary colours, which mix to form tertiary, and so on. stormlight, voidlight, and lifelight could be the primary lights, with towerlight and warlight as two of the secondary lights, and they all need harmonies of their respective rhythms to mix.
3. this might seem a little off topic, but...
in mistborn era 1, sazed mentioned that there are three main aspects of gods in the cosmere: their power/intent, mind/vessel and body. for example, ruin's power or intent was destructive and manipulative abilities (as far as i know till now, i haven't started era 2), his mind or vessel was ati, who was corrupted by the power (i think) and his body was trapped by preservation into beads of atium, which were used by allomancers to access his power... the exact same way the knights radiant use light! by investiture!
so are all forms of light the bodies of the gods/shards? and by investing them the knights radiant gain access to their power? and the mixed light allows them to access more than one shard's power at a time?
i didn't even account for the bondsmiths or the dawnchant yet, because i know next to nothing about them!