SimpleSpectr

SimpleSpectr is a native macOS app built with SwiftUI that renders an interactive spectrogram of any audio file Core Audio can decode — WAV, MP3, AAC/M4A, FLAC, AIFF, ALAC, and more. You can open files from within the app, drag-and-drop them onto the window, launch them via Finder's Open With, or even capture live audio from the microphone for a real-time spectrogram. Low frequencies sit at the bottom and time advances left-to-right, matching conventional audio-analysis conventions. Hovering the cursor reports exact time, frequency, and dB level with a crosshair, while a separate waveform overview lane stays locked to the same time axis and zoom.