From Audiofile Engineering:
Spectre is a multi-instrument real-time audio analyzer for Mac OS X. Designed in Cocoa from the ground up, Spectre proudly takes advantage of Quartz, OpenGL, CoreAudio, and other solid OS X interface features.
Spectre focuses squarely on live audio analysis by offering 17 different multi-channel and multi-trace meters. Each meter can have any number of traces or indicators, and each trace can have it's own number of input channels, mixing, filtering, ballistics and color (including transparency). You can have as many meters (or copies of meters) as your screen will allow! Spectre also gives you very precise control over color gradients.
Spectre is extremely flexible and accurate in its display, utilizing optimized OpenGL, Quartz Extreme and optimzed memory management. Each meter can be resized in realtime without interruption. Every meter has a set of useful factory presets, users may create their ballistics and gradients, and meter settings (or sets of meters) can be saved as files (send them to your friends!).
What's new in this version:
Improves the display of text labels on non-Retina screens.