Show HN: OnKey – I'm a bad singer, so I built an app to show where I'm off-key

OnKey is a Mac app that helps users improve their singing by detecting and scoring their pitch in real-time, using a learned pitch track from a song played once. It's free, open-source, and supports Spotify, Apple Music, and YouTube. However, it has limitations, including difficulty with noisy backing tracks, occasional incorrect note detection, and compatibility issues with older Macs and operating systems.