CD : An Optimal Music Media?

Today, the music media sources are primarily digital (CD, SACD, HDCD, DVD-A).
The only limitations to digital media are the signal truncation (digitalization) and the upper frequency limitation that sampling introduce.

CD material is bandlimited at 22050 Hz, which is way beyond the hearing capabilities of most people (at least for single pure tones!).
The limitation of 22050Hz is introduced by the Nyquist sampling law, which tells us that the upper frequency limit is given by half the sampling rate.
In order to avoid aliasing the recorded signal is low pass filtered so that every part of the signal above 22050Hz is removed, usually by use of high order IIR filters such as Butterworth, Chebychew etc. Unfortunately IIR filters have asymmetrical impulse responses, whereby linear phase characteristics are impossible. This, effectively introduces a varying group delay time.

However, research has shown that this group delay difference is generally inaudible.

The limitation of upper frequency content is unavoidable, but limitation of the low frequency content is only introduced in order to spare us (and especially the loudspeakers) from low frequency noise such as wind introduced by movement of the musicians, pounding footsteps etc.

Limitation of the low frequency content is also done using IIR filters and that is to a much larger extent problematic, since very large group delay times (msecs) hereby are introduced. These delays of certain frequencies are often audible, but unfortunately also unavoidable (if you really need the lower frequency limitation!!!)

Summation: The digital signal sources are potentially good, provided that the music material is mixed by a skilled sound engineer.