In the tune called Whispering we find C-B7-C (I-VII7-I). The melody descends from C to B in bars 2 and 3. The chords also do this. B7 sounds a bit like a dominant chord to me but it uses non-scale tones. B7 is not even a part of the scale. I have been thinking if it is a bit modal but I hear the tune as tonal music. A lot of modal music never use non-scales tones anyway.
How does music theory explain I-VII7-I?