John Chrysostom

"To another various kinds of tongues, to another the interpretation of tongues." 1 Cor 12:10
 "Now the former was thought to be a great gift since it was the first that the apostles received, and the majority of the Corinthians possessed it." (CB, 203)
Here, Chrysostom clearly states that the gift of tongues present in Corinth was the same that the apostles received in Jerusalem at Pentecost (Acts 2), that is, the ability to speak in many different languages.

"For one who speaks in a tongue speaks not to men but to God; for no one understands him, but he utters mysteries in the Spirit." 1 Cor 14:2
"The Corinthians thought that speaking in tongues was a great gift because it was the one which the apostles received first, and with great display. But this was no reason to think it was the greatest gift of all. The reason the apostles got it first was because it was a sign that they were to go everywhere preaching the gospel." (ACCS, 138)
Clearly, the symbolism of universal evangelization would not follow if it was not presumed that the tongues were actual languages (as Acts says they were). The identification of the Corinthians' gift with the apostles' shows that the Corinthians spoke in actual languages, too.

"So with yourselves; if you in a tongue utter speech that is not intelligible, how will any one know what is said? For you will be speaking into the air." 1 Cor 14:9
"If speaking in tongues is useless, why was it given? It was given for the benefit of the person who has it. But if it is to help others also, then there must be some interpretation." (ACCS, 139)
Tongues, to be of any use to the Church as a whole, must be interpreted. Otherwise, they are useless. This is a major reason why they are a lesser gift.

"Tongues are a sign for unbelievers and prophecy for believers." 1 Cor 14:22
"(Paul) does not say that prophecy is useless for unbelievers, but that it is not a sign as tongues are, because it is obviously wasted on them. But neither are tongues of any use for unbelievers. Their only effect is to astound and disturb." (CB, 235)
"What Paul means is this: prophecy is effective among both believers and unbelievers, but when unbelievers and fools hear a strange tongue, they receive no benefit and even mock the speakers as if they were madmen (Acts 2:13). It is only a sign for them, namely, something that perplexes them. But the sign was given that those with understanding might profit from it..." (CB, 236)
Chrysostom explains St. Paul's distinction concerning the usefulness of prophecy and tongues. If not translated into prophecy, the strange tongues will lack in their full effect and only appear as foreign sounds. The hearers will experience astonishment, but ultimately what is uttered is not of much use unless one can translate it.