Music Spectrograph allows you to visually reverse engineer sound and music, in real-time. See a live MIDI piano roll showing pitch and frequency. When playing music files, you can slow down, and even stop sound in time.

Music Spectrograph is being using in college music programs to aid in learning music transcription.

The Hotpaw Music Spectrograph presents a high-resolution scrolling spectrogram as you listen, so that you can see these patterns in sound and music, as well as how sound corresponds to notes on a piano keyboard. This piano alignment makes it far easier to spot which frequencies in sounds correspond to which musical notes.

Features include:
- 12th-octave MIDI-pitch-centered spectrograph (also called a sonogram)
- Usable with live audio, tunes from your iOS device's music library, or a file downloaded via a URL (web address)
- Records up to a 4 minute spectrograph history you can stop, scroll back and review
- Slow Down music files by up to 8X, or speed music up by 3X to skip sections faster
- Stop music in time, and still hear the music frequencies present via re-synthesis (scroll back a little in time to bring up the ReSynth switch).
- Play tunes in mono, left or right channel only, or with center-panned vocals reduced
- Color the pitch graph to see if notes are in-tune or out-of-tune
- Color the spectrograph for loudness, or graph in black-and-white or with Pastel colors
- Mid-pitch filtering to remove some of the higher overtones

Use the Input? button to select a tune from your library (DRM protected iTunes files not supported). Use the Gear button to select among several viewing modes. There's a volume control to manually set the sensitivity threshold. Stop playing or recording to scroll back and review or resynthesize sound. Touch the keyboard during resynthesis to isolate one note.

For many musical sounds, this app will show you many overtones and harmonics, not just the fundamental pitch of notes. Some musical experience is required to tell musical notes from their overtones and harmonic frequencies.