On rare occasions crossing of voices is justified if it improves voice-leading. Do not overlap two adjacent voices unless unavoidable. An overlap occurs between two chords when one voice moves above or below the previous pitch of an adjacent voice. Such motion creates the effect of parallel perfect intervals. Unequal fifths, e.g., P5 to d5, or vice versa, are found and may be used sparingly.
Exceptions are rare.
Otherwise, resolve the 7th down one step if its resolution is a part of the following chord. Borrowed Chords Altered tones are seldom doubled. Otherwise, follow the guidelines for all borrowed chords as they appear in the parallel minor or major keys. Move upper voices in contrary motion with the bass, and avoid chromatic voice-leading in leaving the N 6 . When N 6 proceeds to the tonic chord in second inversion, watch out for parallel 5ths.