If the sound is not of good quality, you may have a phone with an overloaded CPU because it is too old and underperforming. Or you have set a not pleasant combination of the preset (instrument, scale and effects). Tap on the dice icon in the top right, to have the app select the preset combination. When you like it, listen and save a new preset. If the high frequencies bother you, you can lower them with the equalizer in the menu, settings, or deselect the highest frequency octaves, in the scale screen.