Yes, exactly; but, though indeed a correct use of subjunctive voice, it's seldom in my experience that people use this in speech, and again in my experience, it's rare in traditional songs/songs in a traditional idiom   that this grammatical precision is encountered. I wasn't specifically commending the usage (the expression "effective, if defective, communication" was fashionable in Educational systems here about half a century ago), just noting what seemed a peculiarity.