Audio recorded on in HiFi format must be recorded at the same time as the video image and is of quite high quality - certainly far better than the conventional linear audio tracks.  For this reason if one is to use vhs as a timecode master the timecode must be recorded as HiFi audio to insure the best quality recording.  

HiFi VHS can only be played back on a HiFi deck.  It is not to be confused with “stereo” vcrs which have two conventional linear audio tracks.