These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.97 s (backtrack: 0/20).

[ebuild  N     ] media-libs/libresidfp-1.1.1:0/1.1::gentoo  USE="-test" 527 KiB
[ebuild  N     ] media-libs/libsidplayfp-3.0.2:0/7::gentoo  USE="-test -usb" 681 KiB
[ebuild  N     ] media-sound/sidplayfp-3.0.0::gentoo  1014 KiB

Total: 3 packages (3 new), Size of downloads: 2221 KiB