There are four instances of the Present Imperative (Second Person Plural) in the Epistle to the Ephesians where there is ambiguity between the middle and passive voice, because the literal grammatical verb form is identical. (Please click here for more examples in the New Testament.) In the Epistle to the Ephesians, every single one of these four verbs is in the Present Imperative Middle: viz., Be angry! (Eph 4:26); Be not drunk! (Eph 5:18); Be filled! (Eph 5:18); and Be strong! (Eph 6:10). Each verb could therefore be translated with more of the colloquial middle voice than the passive voice: viz., Get angry! Don't get drunk! Get filled! Get strong! The "get" conveys more of the middle voice than the confusion of the passive voice, when something is being done to you. To examine more closely, let us look at this tension in this verse at hand -
Eph 5:18 (GNT)
18 καὶ μὴ μεθύσκεσθε οἴνῳ, ἐν ᾧ ἐστιν ἀσωτία, ἀλλὰ πληροῦσθε ἐν πνεύματι,
There are two imperatives in this verse (both in the present tense and 2nd person plural). The first imperative is not to "get" drunk (negative) and the other is to "get" filled (positive). In English, the word "get" conveys the tension between passive voice and middle voice, such as when we "get" dressed in the morning with our clothing, which leans more toward middle voice than passive voice. So to "get" drunk, does the wine make us drunk (passive voice), or do we "get" drunk by drinking wine (middle voice)? To use a loose but modern analogy, do law enforcement authorities blame the bartender (passive voice), or do they blame the drunk driver (middle voice)? Are we made drunk by the bartender's wine, or do we "get" drunk?
The middle voice is therefore what we find in the context of Eph 5:18, because whether we drink alcohol (and "get" drunk), or whether we yield to the Lord (and "get" filled), the verb voice is not passive, but middle.
Another illustration will help.
When we "get" drunk (with alcohol), we relax our inhibitions of morality and perform deeds consistent with the flesh; however, when we "get" filled (with Spirit) we relax our inhibitions of immorality and perform deeds consistent with the Spirit. That is, when we "get" drunk with alcohol, we do things contrary to our moral nature; when we "get" filled with the Spirit, we do things contrary to our immoral nature.
Thus when the believers at Pentecost spoke in tongues, the confusion with being drunk with alcohol was not because the apostles were speaking in understandable, intelligible and clearly-spoken foreign languages, but because they were proclaiming "the great deeds of God" (Acts 2:11). In other words, when we consider that all these Jewish proselytes from foreign lands heard "the great deeds of God," we must turn to the LXX (Greek Septuagint) and realize that the "great deeds of God" (neuter plural substantive of μεγαλεῖος) are mentioned in the hymns and praises of Ps 71:15-16 in regard to the righteousness of God in forgiving and saving sinners. The Christians of Pentecost were seen as drunk not because of gross moral inhibition, but because of gross immoral inhibition (that is, behaving contrary to their immoral nature) by proclaiming repentance from and the forgiveness of sins.
It is another discussion in its entirely, but if we compare the parallels between the Feast of Weeks (Shavuot) and Pentecost, then we see the "celebration" of the "Great of Deeds of God" in saving his people. (Please click here.) In other words, the songs, hymns, and spiritual songs sung on Shavuot in celebration of the salvation from bondage in Egypt are the direct parallel to "Great Deeds of God" celebrated and proclaimed through the Holy Spirit on Pentecost (salvation from the bondage of sin)...
In summary, we "get" filled with the Spirit (middle voice) when we yield and humble ourselves before the Lord (James 4:6-8) and present ourselves to Him as living sacrifices (dead to the power of the flesh) as noted in Rom 12:1-3. We may do so by singing in our minds and hearts spiritual songs, hymns, and the giving of thanks to the Lord for our salvation and freedom from the bondage of sin.