Show HN: OnKey – I'm a bad singer, so I built an app to show where I'm off-key I'm not a good singer, but strangely enough I still like singing. I've improved a little over time with singing apps, but their song lists are limited by licensing, so I'd often open a song expecting the original and find a cover I didn't want to sing to. So I built OnKey: a free, open-source (MIT) Mac app that listens to whatever you're playing in Spotify, Apple Music or YouTube, learns the singer's melody, and shows you live where you're sharp or flat, with a score at the end. Nightingale did something similar years ago for your own audio files. OnKey works with the music you already stream. Demo (1:35, sound on): https://singonkey.app The first time you play a song, you can sing along while it listens, or play a whole playlist and let OnKey learn the songs in the background before you come back to sing them. When a song finishes it learns the notes on your Mac (a coup...