Tremolo.

This varies the loudness of the track at a very low frequency.

Flanger

Flanging was originally done by slowing down a tape slightly by touching the flange (edge) of the reel. In software, a very short delay (less than 10 msecs) is aplied to the signal, and the delayed signal is then mixed with the main signal. The delay is continuously varied according to a low frequency wave generated in the routine, giving an imitation of a finger applying varying pressure.

Mixing the delayed and main signals gives a comb filter effect, and in a Flanger this is constantly varying.

Chorus

The Chorus is another delay effect. As with the Flanger, the delay is continuously varying, over a range of 20-30msecs. The frequency setting is how fast it varies, and the depth is how much. There is no feedback.

A short delay gives a comb filter, a long delay gives an echo, and the Chorus is somewhere between the two.

Ring Modulator

A Ring Modulator is a way of producing a distorted sound. A signal whose frequency can be set by the user is amplitude modulated by the music signal. This is similar to the way in which an AM radio signal is produced, except that the basic frequency in a radio signal is much higher than the music while the one used in this effect is within the audio range. The result is that extra frequencies (sidebands in radio) appear above and below the musical note. As these are not musical harmonics, the result sounds distorted. Try it.