Step 5: Other options...
And there are many diode types we haven't covered: zener, silicon, other LED colors, etc. Even MOSFET transistors have a voltage drop.
Flipping the asymmetry--switching the directions of all the diodes, will also have an effect. This can emphasize odd or even harmonics. Choose whichever sounds best to you.
There are a great many variations of diode clipping circuits. Here are a few links to get you started... :
-- DIY Fever: Diode Clipping
-- MOSFETs as diodes
-- AMZ - Diode clipping staturation controls
-- AMZ - "Warp" controls--balancing diode clipping
-- AMZ - Mosfets and Zeners as clipping diodes