Using additive synthesis, create the most harmonious, beautiful sound that you can. think about using multiple sin osicllators, with various levels of volume. Be very, very, very careful not to clip your sounds (ie, scale the volumes so that they add up to less then 1.0). Use many oscillators.

Using additive synthesis, create the most evil, terrible, cacophonous and dissonant sound. Again, take care about volume levels.

Using any synthesis technique, attempt to recreate these tones:Dial Tone, Ringing, Cappuccino Machine.