Transruler is a simple iOS Universal app to understand, display and play various musical scales. Transruler makes transcription easy. Transruler provides three rulers. The middle ruler contains all tones and semitones. The top and bottom ruler can each display a selectable scale. You can move each ruler and set the key note independently.
You can play a single note by tapping once. A double tap on a scale ruler plays all notes in this scale. Double tap on the note ruler plays one octave.
This all helps to visualize and learn the relationship between different scales and/or keys.
Transruler supports 16 different scales: