There are also software packages which can analyse a track and add the missing top harmonics.
They are generally called Exciters, or Harmonic Exciters. Only professional mastering engineers will have the proper, top quality versions, though plug-in collectors and gear freaks might have the freeware versions.
I do very often find that I need to use one when transferring Cassette tracks to CD. Otherwise they do sound dull, usually because there are no frequencies above about 12kHz.
Cheers
Dave
(Confessed plug-in collector and gear freak)