, this is a nice introduction in what "gleich" can mean, and it is correct, but in order to avoid confusion one should mention: in "Bereite Dir, Jesu, noch itzo die Bahn." is nothing a native speaker would replace with "gleich" when asked to tell it in other words. The first meaning of "gleich" is "equal" or "same". If you tell me to do something RIGHT NOW I can answer "I'll do it AT ONCE" (or vv) both expressions having to be translated into German as (1st) SOFORT, (2nd) GLEICH (=at the SAME time as I/you tell you/me). However, "noch itzo" might mean "right now" but it can not mean "at once". You wouldn't tell Jesus to come here or go somewhere AT ONCE, would you?
A possible meaning of "noch itzo" is "still now" (even though it might be too late or something like that). If you suggested to have a party at 1:30 AM I might ask you "Jetzt noch?" (= shouldn't this have come to your mind a little earlier?). If I asked you "Jetzt gleich?" this would mean the opposite (can't we wait until 4 AM?).
Things are expressed differently in other languages - aside from different vocabulary. Forget "gleich" in this case here, it will only confuse you.