Actually both MSX1 & 2 had only the same basic sound chip (PSG https://en.wikipedia.org/wiki/General_Instrument_AY-3-8910 https://en.wikipedia.org/wiki/General_

Actually both MSX1 & 2 had only the same basic sound chip (PSG https://en.wikipedia.org/wiki/General_Instrument_AY-3-8910 https://en.wikipedia.org/wiki/General_Instrument_AY-3-8910 MSX2+ & Turbo R also had it for backwards compatibility). The reason why Space Manbow there sounds so much better than Zanac A.I. is that Konami started to put their own sound chip (SCC https://en.wikipedia.org/wiki/Konami_SCC https://en.wikipedia.org/wiki/Konami_SCC) in the cartridges of their later games, which would improve the sound capabilities of the MSX. This is one example of the "plug and play" hardware you mentioned.