Etterna (2016)

A focused option for four-key keyboard practice: set a bookmark or loop a difficult region, change the music rate and inspect the results before another attempt. That combination suits a drummer who wants to work on uneven bursts or hand independence without replaying a long introduction. Etterna is free, but building a suitable community-chart library and setting the audio offset take more initiative than a commercial song menu. Available practice controls and their presentation depend partly on the selected theme.