kouon ha uragoe, teion ha hutuu no koe de utau.

A natural reading is:

こうおん は うらごえ、ていおん は ふつう の こえ で うたう。

Word readings:

• 高音 = こうおん = high notes / high pitch
• 裏声 = うらごえ = falsetto
• 低音 = ていおん = low notes / low pitch
• 普通 = ふつう = normal / ordinary
• 声 = こえ = voice
• 歌う = うたう = to sing

The two は mark two contrasting topics:

• 高音は = as for the high notes
• 低音は = as for the low notes

So the sentence sets up a contrast:

• for high notes, use falsetto
• for low notes, use a normal voice

This is a very common use of は in Japanese: not just topic-marking, but also contrast.

This sentence is a little compressed. A fuller version would be:

高音は裏声で、低音は普通の声で歌う。

In that fuller version, で appears after 裏声 too.

So in the original sentence, the first part is shortened, and the missing で is understood from the second half. Japanese often omits repeated material when it is obvious.

Here, の links 普通 and 声.

• 普通 = normal
• 声 = voice
• 普通の声 = a normal voice

You can think of の here as making 普通 act like a noun modifier, similar to normal voice in English.

This is common with nouns and na-adjective-like words:

• 日本の車 = Japanese car
• 静かな部屋 uses な, but
• 普通の人 = ordinary person

Here, で shows the means / manner / state used to do something.

So:

• 普通の声で歌う = sing with a normal voice / sing in a normal voice
• 裏声で歌う = sing in falsetto

This is the same basic で you see in sentences like:

• 日本語で話す = speak in Japanese
• バスで行く = go by bus

It tells you how the singing is done.

Because Japanese normally puts the main verb at the end of the sentence.

The verb 歌う applies to both parts:

• 高音は裏声で
• 低音は普通の声で歌う

In English, you might repeat the verb more easily, but in Japanese it is very natural to mention it once at the end and let it cover everything before it.

Japanese often leaves out the subject when it is clear from context.

So this could mean things like:

• You should sing high notes in falsetto and low notes in a normal voice.
• I sing high notes in falsetto and low notes in a normal voice.
• One sings high notes in falsetto and low notes in a normal voice.

The exact subject depends on the situation. If this is advice or an instruction, English would probably supply you, but Japanese usually does not need to.

Grammatically, 歌う is the plain non-past form, so by itself it is not an imperative form.

However, depending on context, it can sound like:

• a general statement
• an instruction
• a description of how someone sings

So this sentence could be understood as something like:

• sing the high notes in falsetto, and the low notes in a normal voice
• high notes are sung in falsetto, and low notes in a normal voice

A stronger direct command would look more like:

• 歌え
• 歌って
• 歌いなさい

Both are possible in Japanese, but 高音 and 低音 are more compact and a bit more technical or musical.

• 高音 = high notes / high register
• 低音 = low notes / low register

By contrast:

• 高い音
• 低い音

are more literally high sound and low sound, and can sound a little less specialized.

In a music-related sentence, 高音 and 低音 are very natural choices.

It is usually translated as falsetto, and in many learning contexts that is the best translation.

But the match is not always perfect in every technical vocal sense. In everyday Japanese, 裏声 is the normal word people use for singing in a lighter, higher voice different from the ordinary speaking voice.

So for most learners, it is fine to understand:

• 裏声 = falsetto
• 普通の声 = normal voice

If you want a more singer-specific contrast, you may also see 地声 for the natural chest voice.