Hello BobS5934 and welcome to the forum.

What operating system is your computer running? Your computer operating system provides the default instrument sounds you hear when a midi file is playing. Some programs such as RealPlayer and browsers such as Chrome have additional instrument sounds that they use instead of the default operating system sounds. Also I should point out the more common name in use is patches or instrument patches. I like to use the term instrument sounds because I consider it more descriptive.
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Jim Fogle - 2020 BiaB (734) RB (Build 5) Ultra+ PAK
Cakewalk - Zoom MRS-8 recorder
Desktop: i7 Win 10 build 2004, 12GB ram 256GB SSD, 4 TB HDD
Laptop: i3 64bit Win 10 build 2004, 8GB ram 500GB HDD
Music at: http://fogle622.wix.com/fogle622-audio-home