It's been a while, but I think it goes like this ....
Upsampling does not increase the detail, nor does it increase the bandwidth of the signal, but it alters the sampling frequency, and so it pushes the aliased signals (see Nyquist's theory of sampled signal) to higher frequencies.
This allows the anti-aliasing low-pass filter to have a slower rolloff. It is easier to design a filter with linear phase and lower passband ripple if the rolloff is less steep.
So the whole point of upsampling was to simplify the anti-aliasing low pass filter, so that it causes less degradation to audible frequencies.
Performing any kind of interpolation would be akin to doing some of the filtering in the digital domain. I believe the interpolation bit may be the difference between oversampling (old technology) and upsampling, but I'm not exactly sure.
Upsampling does not increase the detail, nor does it increase the bandwidth of the signal, but it alters the sampling frequency, and so it pushes the aliased signals (see Nyquist's theory of sampled signal) to higher frequencies.
This allows the anti-aliasing low-pass filter to have a slower rolloff. It is easier to design a filter with linear phase and lower passband ripple if the rolloff is less steep.
So the whole point of upsampling was to simplify the anti-aliasing low pass filter, so that it causes less degradation to audible frequencies.
Performing any kind of interpolation would be akin to doing some of the filtering in the digital domain. I believe the interpolation bit may be the difference between oversampling (old technology) and upsampling, but I'm not exactly sure.