Audio tapes record their signal in magnetic domains. These are areas of tape the are large enough to be written and read. Much larger than anything approaching the scale of individual molecules.
Sound recordings on vinly are similarly limited by other factors. To "read" the signal from a record groove a needle is dragged a needle through a v shaped groove. This needle jiggles up and down and left and right, hence the two channels in stereo. The time resolution of the signal (max frequency) is limited by the physics of the jiggling head. It's inertia prevents it from reading signals over a certain limiting frequency. Again, well before the molecular level.
[1] http://en.wikipedia.org/wiki/Film_grain
[edit] - Changed momentum to inertia in the last paragraph.