Adverbs – Using Two ‘-ly’ Adverbs in a Row: Rules and Examples

It seems that two adverbs that both modify one verb can't go one after the other without a conjuction in-between:

• He was speaking slowly unusually.

Meaning to say that he was speaking both slowly and unusually this sounds odd to me whereas the following sentence sounds okay to me:

• He was speaking really quickly.

Since here "really" is actually modifying "quickly". In this case there aren't two adverbs modifying one verb. So two adverbs in a row always follow a structure where the former one modifies the latter one. Based on this you can't have three adverbs in a row.

But if we place a conjuction between the words "slowly" and "unusually" in the first example, then the sentence reads well:

• He was speaking slowly and unusually.

I think if we place a comma the sentence will also read well:

• He was speaking slowly, unusually.

What other ways are there to modify a verb with two or more adverbs other than by placing a comma or a conjuction in-between?

P.s. I've also noticed that some adverbs don't go well with others in this structure:

• He was speaking slowly and unusually interestingly.

The adverb "interestingly" sounds out of place after "unusually", whereas some other adverbs like "well" for instance, sound okay. Or is this odd only to my non-native ear?

Edit: I was thinking of a possibility to modify a verb with a pre-modifier and a post-modifier:

• He was unusually speaking slowly.

But I doubt this is good English since I don't remember coming across such structure.