"Filter" is an abstract class - in other words, a class that you do not use directly. Instead, use one of its subclasses. Many common filters inherit from this abstract class, including LPF, HPF, MoogFF, Ringz, Integrator, Median, LeakDC... and many more.
The Filter class also provides a simple way to visualise the frequency-wise effect of applying a filter, see
Provides a simple way to visualise the frequency-wise effect of applying a filter
Stethoscope.defaultServer.boot // boot the server that will be scoped MoogFF.scopeResponse HPF.scopeResponse BRF.scopeResponse Median.scopeResponse