Vamp is an audio processing plugin system for plugins that extract descriptive information from audio data - typically referred to as audio analysis plugins or audio feature extraction plugins.
Just like an audio effects plugin (such as a VST), a Vamp plugin is a binary module that can be loaded up by a host application and fed audio data. However, unlike an effects plugin, a Vamp plugin outputs not processed audio but some sort of symbolic information. Typical things that a Vamp plugin might calculate include the locations of moments such as note onset times, visual representations of the audio such as histograms, or curve data such as power or fundamental frequency.
Hosts using Vamp plugins include Audacity and Sonic Visualiser.
This package contains C and C++ header files for developing Vamp plugins and hosts as well as source code of example plugins and a simple host.