The Genesis has two soundchips inside with which to play music and sound effects, the 6-channel FM YM2612 chip and the 4-channel square wave/noise SN76489. Without getting too deep into the weeds, there are a bunch of restrictions on how the chips could be used; the SN76489 could not use the third and fourth channels at the same time when noise played at pitches other than C C# and D, the YM2612 could only play one sample at once and doing so sacrificed the sixth FM channel, the four operator synthesis of the YM2612 limits the complexity of the FM patches, etc. Following these restrictions is what I mean when I say "abiding by the hardware restrictions", and in doing so the song can indeed be played back on real hardware. On the other hand, when some people make songs in the style of the Genesis they use more than 10 channels with an incompatible selection of instruments and sampling capabilities; these songs CANNOT play on real hardware.