Rather simplistically, I should answer as follows...
A few questions about "atonality":
What is it?
Basically it is music that proceeds in a manner whereby it maintains no loyalty whatsoever to a particular tonic. This will require, for instance, the abandonment of harmony that is what might be termed "functional" (in the traditional sense).
Does it exist in the mind of the composer - who is free to ignore tonal relationships as he composes?
It is more likely that composers providing such examples are working completely outside conventional harmonic idioms, and thereby never conceptualize their output in terms of these. In that sense they are not actively avoiding tonality, but rather simply not thinking of it.
Does it then necessarily also exist in the mind of the listener, or is he allowed to perceive tonal relationships while listening to an "atonal" piece?
If the piece is truly atonal one must suppose that there will not in fact
be any tonal relationships to be perceived by the listener. (If there are, then it cannot be "atonal".) But there can surely never be any restrictions (or censorship) imposed upon listeners who are, of course, entirely free always to listen to the music in their own way.
Does it exist at all?
Certainly!
Does atonality - if it exists - necessitate any particular scale or system of temperament?
Since the varying examples of tonality that arose over many centuries required differing temperaments and scale systems, it must be supposed that the absence of tonality thereby removes altogether the need for these. In fact most atonalists simply accept the 12-tone Equally Tempered scale (probably simply because that was the one they inherited). But some did not, and asked for different tuning systems, ranging from purely attuned intervals throughout to the use of microtones. Their use of these however was non-tonal ("atonal") and supposedly more concerned with colours and textures.
Why did Schönberg himself reject the word "atonality"? And why, despite that, do critics persist in ascribing that quality to many of his works?
Because (probably for pedantic reasons) he applied the term "tonal" to music that employed the interval of
a tone - rather than to music that, in employing tones, did so in a manner that placed their use in direct relationship to a
key centre. The term "tone" has always been ambiguous throughout the history of music theory, and even very early theorists often found it necessary to explain that they were using the term
tonus variously as "mode", "melody", and "discrete interval with the ratio 9/8". It later also became adopted (especially in the US) to mean simply "note". So these ambiguities were helpful to Schönberg in rejecting a term that might otherwise have implied that
something was now lacking from his music (instead of a novelty and innovation having been added).
What is "pan-tonality"?
Pan-tonality is, it seems to me, just a particular kind of 'atonality' wherein the absence of loyalty to a
particular key arises not (as in other types) by the absence of key as such, but rather rejects the idea of 'home key' by freely and at will moving through many keys and thereby preserving an overall sense of rhapsodic 'tonal instability'.
Can members cite any favourite examples of atonality?
I have no particular favourite example of any of the above to cite (although I have experienced a wide range of different examples)
