Many popular stereo recordings are intentionally mixed with most insturments and vocals coming equally from both channels - mostly 'dual mono' with just 'sprinklings' of some instruments coming from either the left only or right only. This is a convention that sucks for people who like good sound, but the 'masses' will be assured of hearing all the instruments no matter how messed up their speaker placement is. It's a holdover from the days of LPs. If an identical signal is panned equally to the left and right speakers, there will be a 'phantom' image created sharply in the middle.

One thing that is becoming very common is the use of 'spatializer' type processing which can image instruments out into the room, even behind you. With properly set up speakers, these can sound amazing, but these effects are created by intentional introduction of out of polarity signals, which can sound strange in some instances. Maybe this is what you are hearing, as it can sound like there's a hole-in-the-middle on certain instruments, even though the vocals and other instruments image sharply in the middle.

DVD-A and SACD have no baggage from LPs, so the mixes can be more creative, with wider soundstages front and back. It is still not unheard of for some instruments and vocals to be panned into all three front speakers to varying degrees.

Classical and Jazz recordings tend to have a wider soundstage in stereo, as natural sound is more valued.

[This message has been edited by soundhound (edited December 29, 2002).]