If I understand Janie (14 Oct 11 - 10:25 PM) correctly, a single file resp. its bit-by-bit copy sound differently depending on the player software. The mail is innocent.

Some player software may try to "enhance" its playback, or adapt it to an assumed device context, e.g. surround. Sound hardware may do the same, depending on how it is addressed by the software.

For serious music (studio or garage), you should run through all "Options", "Settings" and "Extras" of your playing software and of your sound card driver (accessible via the operating system). Switch off all fancy features - which may also eat up system performance.

Compression: don't confuse data compression (e.g. MP3) with dynamic compression, which are two completely different things. The former makes for quicker mailing and slightly diminishes the quality of studio recordings, inaudible in "garage" recordings.