Ο κιθαρίστας, ο ντράμερ και ο μπασίστας παίζουν μαζί.

Because each noun is a separate definite noun phrase:

• ο κιθαρίστας = the guitarist
• ο ντράμερ = the drummer
• ο μπασίστας = the bassist

In Greek, when you list definite nouns, it is very common to repeat the article before each one. This sounds natural and clear.

So:

• Ο κιθαρίστας, ο ντράμερ και ο μπασίστας...

is a very normal way to say the guitarist, the drummer, and the bassist...

Each person in the list is singular, but together they form a plural subject:

• the guitarist
• the drummer
• the bassist

Since all three people are doing the action, Greek uses the 3rd person plural verb form:

• παίζουν = they play / are playing

This works just like English:
The guitarist, the drummer, and the bassist play together.

Παίζουν is the 3rd person plural present of παίζω (to play).

A few useful forms are:

• παίζω = I play
• παίζεις = you play
• παίζει = he/she/it plays
• παίζουμε = we play
• παίζετε = you all play
• παίζουν = they play

Here it matches the plural subject, so παίζουν means they play.

Yes. The verb παίζω is used for playing music/instruments, but also for playing games or playing in general, depending on context.

In this sentence, because the subject is:

• the guitarist
• the drummer
• the bassist

it clearly means they play music.

Μαζί means together.

So:

• παίζουν μαζί = they play together

Its position is very natural here. Greek adverbs are often quite flexible, but putting μαζί after the verb is common and straightforward.

Ντράμερ is a loanword from English drummer. Modern Greek uses many borrowed words for music, technology, and pop culture.

So this sentence mixes standard Greek grammar with some borrowed vocabulary:

• κιθαρίστας = guitarist
• ντράμερ = drummer
• μπασίστας = bassist

Even when a word is borrowed, Greek still gives it grammatical features like gender and article:

• ο ντράμερ

You can tell mainly from the article ο, which is the masculine singular definite article in the nominative case.

So:

• ο κιθαρίστας
• ο ντράμερ
• ο μπασίστας

are all masculine singular subjects.

Also, endings like -ας often appear in masculine nouns, as in:

• κιθαρίστας
• μπασίστας

For ντράμερ, the ending does not show gender clearly, so the article ο is especially helpful.

Because Greek is listing three individual people, not using one plural noun.

This sentence is structured as:

• the guitarist
• the drummer
• and the bassist

Each one is singular by itself, so each gets singular article + singular noun.

If you used οι, that would mean the for a plural noun phrase, which is not what is happening here.

They are in the nominative case, because they are the subject of the sentence.

You can see that from the article:

• ο = masculine singular nominative

So:

• ο κιθαρίστας
• ο ντράμερ
• ο μπασίστας

are all nominative subjects.

Yes. The commas separate items in a list, just as in English:

• Ο κιθαρίστας, ο ντράμερ και ο μπασίστας...

Greek punctuation is very similar to English in this kind of sentence. The final και (and) introduces the last item of the list.

In modern Greek spelling, these letter combinations often represent sounds that match borrowed words:

• ντ often sounds like d
• μπ often sounds like b

So:

• ντράμερ sounds roughly like dramer
• μπασίστας sounds roughly like basistas

This is very common in borrowed vocabulary.

Yes, Greek word order is more flexible than English, although this version is the most neutral and natural:

• Ο κιθαρίστας, ο ντράμερ και ο μπασίστας παίζουν μαζί.

You might also hear variations depending on emphasis, but for a learner, this is the best standard pattern to use:

subject + verb + adverb

So:

• [the guitarist, the drummer, and the bassist] + [play] + [together]