gasareul miri oewosseo.

가사 means lyrics. The -를 is the object particle, marking 가사 as the thing being memorized.

• 가사 = lyrics
• 가사를 = the lyrics, as the object of the verb

So in this sentence, 가사를 tells you what was memorized.

It can be either, depending on context. Korean nouns usually do not change form for singular vs. plural the way English nouns do.

So 가사 can mean:

• a lyric / the lyrics
• more naturally in English here: the lyrics

Even though English uses the plural word lyrics, Korean just uses 가사.

미리 means in advance, beforehand, or ahead of time.

It is an adverb, so it describes how/when the action was done. In Korean, adverbs often come before the verb:

• 가사를 미리 외웠어. = memorized the lyrics beforehand

You could also see 미리 earlier in the sentence for emphasis, such as:

• 미리 가사를 외웠어.

Both are natural.

외웠어 comes from the dictionary form 외우다, which means to memorize or to learn by heart.

Breakdown:

• 외우다 = to memorize
• 외웠어 = memorized / learned by heart

This is the past tense casual form.

A rough contraction process is:

• 외우 + 었어
• 외우었어
• 외웠어

So 외웠어 means memorized.

외우었어 is the full underlying form, but Korean usually contracts it in normal speech and writing:

• 외우었어 → 외웠어

This kind of contraction is very common and natural. Learners often see the shorter form much more often than the fully expanded one.

외웠어 is in the casual/informal speech style. It is used with:

• close friends
• younger people
• someone you can speak casually with
• inner monologue / diary-style narration

More polite versions would be:

• 가사를 미리 외웠어요. = polite
• 가사를 미리 외웠습니다. = formal

So the sentence as written sounds casual.

Korean often omits the subject when it is clear from context.

So 가사를 미리 외웠어. could mean:

• I memorized the lyrics beforehand.
• He memorized the lyrics beforehand.
• She memorized the lyrics beforehand.
• They memorized the lyrics beforehand.

The actual subject depends on the situation. In Korean, leaving it out is very normal.

Korean is generally a subject-object-verb language, so the verb usually comes at the end of the sentence.

This sentence follows that pattern:

• 가사를 = object
• 미리 = adverb
• 외웠어 = verb

So the final verb placement is completely normal in Korean.

외우다 specifically means to memorize or to learn by heart.

Compare:

• 외우다 = memorize
• 배우다 = learn
• 기억하다 = remember

So if someone studied the lyrics until they knew them by heart, 외우다 is the best choice.

For example:

• 가사를 배웠어 = learned the lyrics
• 가사를 기억했어 = remembered the lyrics
• 가사를 외웠어 = memorized the lyrics

The sentence uses 외우다 because it focuses on the act of committing the lyrics to memory.

Yes, but the meaning or emphasis would change.

• 가사를 미리 외웠어.
  This is the most neutral way to say memorized the lyrics beforehand.

• 가사는 미리 외웠어.
  This gives 가사 topic or contrast emphasis, something like:
  As for the lyrics, I memorized them beforehand
  or
  I memorized the lyrics beforehand, at least

So -를 is the normal object marker here, while -는 adds topic/contrast nuance.

It is pronounced roughly like weo-sseo in standard Korean romanization terms.

A learner-friendly approximation is:

• 외웠어 ≈ weh-wuh-suh or weo-sseo

Important points:

• 외 is usually pronounced like 웨 in modern Korean
• 웠어 sounds like wo-sseo / weo-sseo

So the whole sentence sounds roughly like:

• 가사를 미리 외웠어
• ga-sa-reul mi-ri weo-sseo

Exact pronunciation can vary a little depending on speaker and speed.