Questions & Answers about Es audaz mezclar lo retro con lo moderno.
Since the current lesson is about a lo phrases, why don't we say mezclar a lo retro?
The phrase a lo + adjective means "in a [blank] way" or "in the style of" (it acts as an adverb describing how an action is done). If you said mezclar a lo retro, it would mean "to mix in a retro way." Here, we aren't describing how the mixing is done; we are talking about the things being mixed: "the retro" and "the modern." To turn an adjective into an abstract noun like this, we just use lo + adjective.
Why do we use the neuter article lo instead of el or la for retro and moderno?
The neuter article lo turns an adjective into an abstract noun that represents a general concept, category, or quality. Lo retro translates to "retro things in general" or "that which is retro." If you used el or la, it would imply a specific, omitted noun that you were referring back to (such as el estilo retro or la época moderna).
I noticed retro doesn't end in -o or -a. Does it ever change its form to match gender or number?
No, retro is an invariable adjective in Spanish. It is originally a prefix that became popular as a standalone word, so it never changes to match gender or number (for example, las camisas retro). Moderno, on the other hand, is a standard adjective and does change (las camisas modernas). In this sentence, both are paired with the neuter singular lo, so they take their default masculine/neuter singular forms.