Here are the classes, structs, unions and interfaces with brief descriptions:

NVamp
NHostExt
CPluginBufferingAdapter	PluginBufferingAdapter is a Vamp plugin adapter that allows plugins to be used by a host supplying an audio stream in non-overlapping buffers of arbitrary size
CPluginChannelAdapter	PluginChannelAdapter is a Vamp plugin adapter that implements a policy for management of plugins that expect a different number of input channels from the number actually available in the source audio data
CPluginInputDomainAdapter	PluginInputDomainAdapter is a Vamp plugin adapter that converts time-domain input into frequency-domain input for plugins that need it
CPluginLoader	Vamp::HostExt::PluginLoader is a convenience class for discovering and loading Vamp plugins using the typical plugin-path, library naming, and categorisation conventions described in the Vamp SDK documentation
CPluginSummarisingAdapter	PluginSummarisingAdapter is a Vamp plugin adapter that provides summarisation methods such as mean and median averages of output features, for use in any context where an available plugin produces individual values but the result that is actually needed is some sort of aggregate
CPluginWrapper	PluginWrapper is a simple base class for adapter plugins
CFFT	A simple FFT implementation provided for convenience of plugin authors
CFFTComplex	A simple FFT implementation provided for convenience of plugin authors
CFFTReal	A simple FFT implementation provided for convenience of plugin authors
CPlugin	Vamp::Plugin is a base class for plugin instance classes that provide feature extraction from audio or related data
COutputDescriptor
CFeature
CPluginAdapter	PluginAdapter turns a PluginAdapterBase into a specific wrapper for a particular plugin implementation
CPluginAdapterBase	PluginAdapter and PluginAdapterBase provide a wrapper class that a plugin library can use to make its C++ Vamp::Plugin objects available through the Vamp C API
CPluginBase	A base class for plugins with optional configurable parameters, programs, etc
CParameterDescriptor
CPluginHostAdapter	PluginHostAdapter is a wrapper class that a Vamp host can use to make the C-language VampPluginDescriptor object appear as a C++ Vamp::Plugin object
CRealTime	RealTime represents time values to nanosecond precision with accurate arithmetic and frame-rate conversion functions
C_VampFeature
C_VampFeatureList
C_VampFeatureUnion
C_VampFeatureV2
C_VampOutputDescriptor
C_VampParameterDescriptor	C language API for Vamp plugins
C_VampPluginDescriptor
CAmplitudeFollower	Example plugin implementing the SuperCollider amplitude follower function
CFixedTempoEstimator	Example plugin that estimates the tempo of a short fixed-tempo sample
CD
CPercussionOnsetDetector	Example plugin that detects percussive events
CPlugin	Vamp::Plugin is a base class for plugin instance classes that provide feature extraction from audio or related data
COutputDescriptor
CFeature
CPluginHostAdapter	PluginHostAdapter is a wrapper class that a Vamp host can use to make the C-language VampPluginDescriptor object appear as a C++ Vamp::Plugin object
CPluginInputDomainAdapter	PluginInputDomainAdapter is a Vamp plugin adapter that converts time-domain input into frequency-domain input for plugins that need it
CPluginLoader	Vamp::HostExt::PluginLoader is a convenience class for discovering and loading Vamp plugins using the typical plugin-path, library naming, and categorisation conventions described in the Vamp SDK documentation
CPluginWrapper	PluginWrapper is a simple base class for adapter plugins
CPowerSpectrum	Example plugin that returns a power spectrum calculated (trivially) from the frequency domain representation of each block of audio
CRealTime	RealTime represents time values to nanosecond precision with accurate arithmetic and frame-rate conversion functions
CSpectralCentroid	Example plugin that calculates the centre of gravity of the frequency domain representation of each block of audio
CZeroCrossing	Example plugin that calculates the positions and density of zero-crossing points in an audio waveform