Bas ses grubu tek sesmişçesine birlikte şarkı söyledi.

Bas ses grubu means the bass vocal group / the bass section.

• bas = bass
• ses = voice / sound
• grup = group

The form grubu is not random. In Turkish noun compounds, the second noun usually takes a compound suffix:

• ses grubu = voice group
• öğrenci kartı = student card
• şehir merkezi = city center

So bas ses grubu is a normal compound structure. The -u here is part of that structure, not an object marker.

It means as if it were a single voice or as though they were one voice.

This describes how the group sang: so closely and smoothly that they sounded like just one voice.

A more expanded, easier-to-see version would be:

• tek bir sesmiş gibi
• sanki tek bir sesmiş gibi

So tek sesmişçesine is a more compact and literary way to express that idea.

Not really in the normal sense.

Yes, it comes from the same form you know from -miş, but here you should understand the whole expression -mişçesine as a unit meaning as if / as though.

So don’t read it as a literal past tense like it had been one voice. In this sentence, it is part of a comparison:

• tek sesmişçesine = as if it were one voice

Both are possible.

Turkish often leaves out bir when tek already makes the meaning clear, because tek already means single / one.

So:

• tek ses = one voice / a single voice
• tek bir ses = a single voice

The version with tek bir ses can sound a little more explicit or emphatic, but tek ses is completely natural.

Birlikte means together.

Even though grup already refers to multiple people, birlikte still adds useful emphasis. It highlights that they were acting in coordination, not just that a group happened to be singing.

So the sentence is not only saying the bass group sang, but also that they sang together, in unison, almost like one voice.

Yes, word-for-word it looks like said a song, but in Turkish şarkı söylemek is the normal verb phrase meaning to sing a song.

This is just how Turkish expresses the idea. Many languages use verb+noun combinations where English uses a single verb.

So:

• şarkı söylemek = to sing
• şarkı söyledi = sang / sang a song

In this expression, söylemek is understood as to perform vocally, not simply to say.

Because the sentence is talking about the action of singing, not about one specific song already identified in the conversation.

In Turkish:

• şarkı söyledi = sang / sang a song
• şarkıyı söyledi = sang the song

So the bare form şarkı is natural when the object is indefinite or when the focus is on the activity itself.

Because the grammatical subject is bas ses grubu, which is singular: the bass group.

Even though the group contains several people, Turkish treats grup as one singular subject, so:

• Bas ses grubu ... söyledi. = correct and natural

This is similar to English sentences like The choir sang beautifully. Many people are involved, but the subject is still one unit.

It is understandable and correct, but it sounds somewhat literary, expressive, or elevated.

In everyday speech, many speakers would more naturally say:

• tek bir ses gibi
• tek bir sesmiş gibi
• sanki tek bir ses gibi

So the original sentence has a slightly more polished or stylistic feel than very casual spoken Turkish.