Editing Low And High Pass Filters
In addition to changing the volume and pan of a sound over time, Mixcraft allows you to change the low pass and high pass filter over time.

What Is A Low Pass Filter?
A low pass filter is an audio filter that literally allows low frequencies to 'pass' while removing (or 'filtering out') high frequencies.  A low-pass filter has a cutoff value, such that every frequency below the cutoff can be heard, and every frequency above the cutoff is reduced or removed entirely from the audio.  For example, if you use a low-pass filter with a cutoff frequency of 2000 Hz, every frequency below 2000 Hz will be heard in full, but every frequency above 2000 Hz will be reduced or removed entirely.

The low pass filter in Mixcraft is a resonant filter.  This means that in addition to the cutoff value, there is also a value for the amount of resonance.  Simply put, resonance involves emphasizing frequencies at the filter's cutoff point.  So, if we imagine a filter with a cutoff frequency of 2000 Hz and a high resonance value, what will be heard is a sound where frequencies above 2000 Hz have been removed, frequencies below 2000 Hz remain the same, and frequencies at and directly around 2000 Hz are louder.  Resonance is a simple concept, but it can be a dramatic effect, especially if resonance is high and the filter's cutoff frequency is changing.  This effect is what's known as a 'filter sweep'.

Every sound in Acoustica Mixcraft has its own resonant low-pass filter.  These filters can be used in many ways.  You can use them as an EQ effect, reducing certain high frequencies such as acoustica guitar finger squeaks.  Or, you can use them to create filter sweeps, by adding resonance while the cutoff frequency moves up or down.  The cutoff frequency and resonance amount are each controlled via an envelope, and these values can change over time, in the same way a volume or pan envelope can be used to change to volume and pan amount over time.

How To Edit A Low Pass Filter
To edit a sound's low pass filter cutoff, go to the toolbar and make sure that Low Pass Cutoff is selected.  By default, all points on this envelope are at 100%, meaning that all sounds below the cutoff (i.e. everything) can be heard.  Adding points lower than 100% will cause high frequencies to be increasingly removed from the audio.

To edit a sound's low pass filter resonance, go to the toolbar and make sure that Low Pass Resonance is selected.  By default, all points on this envelope are at 0%, meaning that there is no resonance/emphasis at the cutoff point.  Adding points higher than 0% will cause emphasis at the cutoff frequency, if any frequencies exist at and around that frequency.

What Is A High Pass Filter?
A high pass filter is the exact opposite of a low pass filter, meaning that high frequencies above the cutoff point are allowed to pass, while frequencies below the cutoff point are reduced or removed.

The high pass filter in Mixcraft is also a resonant filter.

How To Edit A High Pass Filter
To edit a sound's high pass filter cutoff, go to the toolbar and make sure that High Pass Cutoff is selected.  By default, all points on this envelope are at 0%, meaning that all sounds above the cutoff (i.e. everything) can be heard.  Adding points above 0% will cause low frequencies to be increasingly removed from the audio.

To edit a sound's high pass filter resonance, go to the toolbar and make sure that High Pass Resonance is selected.  By default, all points on this envelope are at 0%, meaning that there is no resonance/emphasis at the cutoff point.  Adding points higher than 0% will cause emphasis at the cutoff frequency, if any frequencies exist at and around that frequency.

What Famous Examples Of Music Have This Effect?
Many songs in many genres take advantage of resonant filter sounds.  The opening note to the Rush song Tom Sawyer contains a famous resonant low pass filter sweet of a synthesizer sound.  Many dance songs begin with a low pass filter whose cutoff frequency is slowly rising, so the song starts off muted and suddenly is full and bright.