Fact is the chair is part of the room and everything in the room affects acoustics and sound.
How much the chair will matter in practice will of course vary. In many cases probably not to any noticeable extent.
However if teh chair is tall and directly behind your ears that alone can have a significant difference in what you hear due to sound reflected there.
if you do not believe me try a simple test. Listen to your hifi normally. Then cup your hands behind your ears and listen. you will hear a difference, probably for the better, particularly in the midrange which is where most music occurs. Changing the location and form of the cupped hands will alter the sound you hear as well.
