Mater dicit lyram suaviorem esse, sed pater citharam clariorem audiri.

Because Latin is using indirect statement after a verb of saying.

After dicit, Latin often uses:

• accusative subject
  • infinitive

So:

• lyram suaviorem esse = literally the lyre to be sweeter / more pleasant
• citharam clariorem audiri = literally the cithara to be heard more clearly / more distinctly

Even though lyram and citharam are the logical subjects of esse and audiri, in this construction they appear in the accusative.

It is an accusative-and-infinitive construction, the standard Latin way to express reported speech or thought.

You can break it down like this:

• lyram = accusative subject
• suaviorem = predicate adjective agreeing with lyram
• esse = infinitive

So the structure means:

• [Mother says] the lyre is more pleasant-sounding

Latin does not normally use that + a finite verb here, the way English does. Instead of Mother says that the lyre is..., Latin prefers Mother says the lyre to be...

They are both comparative adjectives.

• suaviorem comes from suavis = pleasant, sweet
• clariorem comes from clarus = clear, bright, and in sound-related contexts often clearer or louder / more distinct

Their endings show that they are:

• feminine
• accusative
• singular

They agree with:

• lyram → suaviorem
• citharam → clariorem

So the grammar is simple agreement: the adjective matches the noun it describes.

Because Latin does not always need to state the second half of the comparison explicitly.

A comparative adjective like suaviorem or clariorem can mean simply:

• more pleasant
• clearer
• louder
• more distinct

without saying exactly than what.

In this sentence, the comparison is probably understood from the context, especially because the two instruments are being contrasted:

• mother prefers the lyra
• father prefers the cithara

So the missing comparison is easy to infer.

Because the two clauses are expressing slightly different ideas.

First clause

• lyram suaviorem esse
• literally: the lyre to be more pleasant

This uses esse because suaviorem is a predicate adjective describing what the lyre is like.

Second clause

• citharam clariorem audiri
• literally: the cithara to be heard more clearly / distinctly

Here the idea is not just what the cithara is, but how it comes across when heard. So Latin uses audiri, the passive infinitive of audire.

This is a very natural Latin way to express perceived quality.

Because the cithara is the thing being heard, not the one doing the hearing.

• audire = to hear
• audiri = to be heard

So:

• citharam audiri = the cithara to be heard

If Latin used the active infinitive audire, it would mean:

• the cithara to hear

which would make the cithara the hearer, and that does not fit the sentence.

Yes, very likely.

The full sense is:

• Mater dicit lyram suaviorem esse, sed pater [dicit] citharam clariorem audiri.

Latin often omits a repeated verb when it is easy to understand from the previous clause. This is a common stylistic feature.

So the second half means:

• but father says the cithara is heard more clearly

with dicit understood.

Yes. Grammatically, clariorem agrees with citharam.

That means Latin is directly describing the instrument as:

• clearer
• more distinct
• possibly louder

from the listener’s point of view.

English often shifts this idea and says something like:

• the cithara sounds clearer
• the cithara is heard more clearly
• the sound of the cithara is clearer

Latin can express that idea more directly by making the adjective agree with the instrument itself.

The word order is quite natural for Latin and also helps create contrast.

You can see the pairing:

• Mater ... lyram ... suaviorem
• pater ... citharam ... clariorem

This sets up a neat opposition between:

• mother vs. father
• lyra vs. cithara
• suavier vs. clearer

Also, Latin often puts infinitives such as esse and audiri toward the end of their clauses. So the overall order is flexible, but not random.

Probably this one:

After a verb of saying, Latin often uses accusative + infinitive

In this sentence:

• dicit lyram suaviorem esse
• [dicit] citharam clariorem audiri

That pattern is extremely common in Latin, especially after verbs meaning:

• say
• think
• know
• hear
• report

So this sentence is a good example of a core Latin structure that English speakers need to get used to early on.