A free and open-source web app for working out music by ear: play a track at any speed from 10% to 150% with the pitch untouched, loop the bar you are stuck on, pin reference notes on the spectrogram and hear them, and mark the spots you care about. It is an alternative to Seventh String Transcribe!, with which it is not affiliated, and it runs entirely in the browser: the audio file never leaves your machine.