A passage often cited by evangelicals to prove that every cultural expression is legitimate since people from every nation will be admitted into heaven is Revelation 5:9:
And they sang a new song, saying, ‘Worthy are you to take the scroll and to open its seals, for you were slain, and by your blood you ransomed people for God from every tribe [phylēs] and language [glōssēs] and people [laou] and nation [ethnous].1
Here John uses four terms related to ethnic identity, but it is important to recognize that John uses the terms not to emphasize cultural distinctions between various people groups but rather to signify all peoples without national or cultural distinctions. For example, Mounce states of the terms in this verse, “It is fruitless to attempt a distinction between these terms as ethnic, linguistic, political, etc. The Seer is stressing the universal nature of the church and for this purpose piles up phrases for their rhetorical value.”2 Likewise, Thomas argues, “The enumeration includes representatives of every nationality, without distinction of race, geographical location, or political persuasion.”3
In other words, terms like ethnos, (“race”), phylē (“tribe”), glōssa (“language”), and laos (“people”) do not refer to the culture (behavior) of people, but rather to the people themselves, and ethnic distinctions among people in heaven will be absent.
MacLeod summarizes common definitions for such race-related terms:
(1) The word “tribe” (phylē) denotes “a group bound together by common descent or blood-relationship.” In the New Testament most references are to the tribes of Israel. In Revelation 5:9 the word includes the redeemed from the Gentile world, which also includes tribal groups (Christian Maurer, “φυλή,” in Theological Dictionary of the New Testament, vol. 9 , 245–50, esp. 245, 250). Bauer, Arndt, and Gingrich say that φυλή means “a subgroup of a nation characterized by a distinctive blood line, tribe” (A Greek-English Lexicon of the New Testament and Other Early Christian Literature, 1069). (2) “Tongue” (glōssa) refers to a people group distinguished by their language (Johannes Behm, “γλῶσσα,” in Theological Dictionary of the New Testament, vol. 1 , 722). (3) “People” (laos) speaks of a race, that is, “a body of people with common cultural bonds . . . a people-group” (Bauer, Arndt, and Gingrich, A Greek-English Lexicon of the New Testament and Other Early Christian Literature, 586). (4) “Nation” (ethnos) means “a body of persons united by kinship, culture, and common traditions” (Ibid., 276).4
Indeed, the New Testament perspective on race seems to be that of eliminating racial distinctions rather than highlighting them. The use of another term related to race, Hellēn (“Greek”), illustrates this point. According to Paul, in Christ there is no distinction between Jew and Greek (Gal 3:28; Col 3:11; 1 Cor 12:13). Rather, all are united into one newly distinct body.
These examples of the use of terms related to ethnic identity by New Testament authors indicate that the terms signify distinct groups of people that unify around common heritage, geographical location, language, and/or custom. “Culture” as defined by contemporary anthropologists may be one of the elements around which an ethnos unifies, but an ethnos is not “culture” itself. Similarly, phylē is not a lineage, it is a people united by lineage; likewise, although glōssa is often used to specifically designate languages, in these cases it is used metaphorically to signify people united by a common language; in the same way laos and ethnos identify groups united by politics or culture, but they do not equal culture itself.
Thus, while it is certainly possible (and even probable) that lots of different kinds of cultural expressions will be present in the worship of heaven, there is not Scriptural proof of this, and there is certainly no proof that all cultural expressions will be there. For one thing, it is at least instructive to note that at least one aspect of cultural diversity is eliminated in this heavenly picture–their clothing (Rev 7:9). All of these people from various tribes, peoples, and nations are wearing the same thing: white robes. Where is the cultural diversity in that?
So while I would never assert with certainty that there will be only one kind of musical expression in heavenly worship, the fact that all people are wearing the same thing at least allows for that possibility. I should also quickly say that I have no idea what that worship will sound like; my guess is that it will be distinct from anything we know here on earth, but that is only a guess.