Company Spectral Efficiency Ltd created these great apps:
ScaleHelper, Jazz ScaleHelper, ScaleHelper Lite, Jazz ScaleHelper Lite, Note Hitter, Note Hitter Lite, Play Scales, Play Scales Lite, Note Hitter Voice, Note Hitter Voice Lite, Note Hitter TAB, Note Hitter TAB Lite, ScaleHelper for iPad, Jazz ScaleHelper for iPad, and others..
