Thanks for the detailed explanation, Boing4000, I really appreciate it because it's complete yet easy to understand
However, I never noticed any note skipping on my Amiga 1200 (stock 14Mhz 68020), even with Amiga 500 games. For example, Loom, Waxworks and Monkey Island played great in this machine and they sound as intended without any skipped notes.
What I'm trying to say is that maybe a 14 Mhz-TURBO version would make these skips less frequent to almost inexistant, and would make a great compromise: great speed (almost twice faster than stock 7Mhz Amiga 500, I know it's not exact) while mantaining good sound.
In the "7 OR 50Mhz" situation we're in "one or the other!" situation.
Moreover, some games are prepared for higher clock speeds (Monkey Island: intro clouds only appear in 14+ Mhz Amigas, Loom: has smooth animation in 14+ Mhz Amigas) but at the same time they have broken sound with the 50 Mhz "excessive" speed. 14Mhz would make a perfect compromise: good sound, no skipped notes (I know them pretty well on A1200), with fast and smooth animations.