The following description paraphrases Bowie's Producer Tony Visconti:
Each mic was linked to a gate set to open only when the signal was within a certain range. If Bowie sang softly, only the close mic was operational; at medium volume, the second mic ten feet away kicked in; full-throated singing would open up the third gate. The effect, which can easily be heard on the title track of Heroes, is to add more room tone (natural ambience) the more the singer projects. The effect is not the same as simple reverb; the gate cuts off the reverb tail, so that what the listener is left with is a strange, otherworldly quality to the vocal.
- From Virgil Moorefield's The Producer as Composer (2005/2010, p. 52)
Bowie had this to say about his performance of "Young Americans" (recorded at Sigma Sound Studios in Philadelphia) in the 1995 PBS documentary "Make it Funky":
"I kind of, you know, tried to do my own version of my interpretation of that kind of music and it wasn't authentic at all. I think my stage movements kind of resembled a rather spindly wooden top, I think was kind of my version of James Brown movement"
I'd argue it has its own kind of authenticity...(dancing is @ 4:20 in the video below)
From Tony Vicsonti's autobiography (2008), paraphrasing Bowie before the making of Low in 1976:
"Look Tony, before we start recording I have to say this is strictly experimental, and that nothing might come of it in the end. Are you prepared to maybe erase a month of your time?"
Visconti goes on to say:
"True to form there were no melodies or lyrics, just grooves and chord changes. David called them 'demos' but I recorded them carefully, knowing full well that these could end up as masters, and they did."