Best by far and I have tried many

Stunning free app
Developers give user control to use their own favorite music
This one feature is worth paying for
Even the most expensive apps dont offer this perfect feature
The tones work best if one is inspired to listen to them in the first place
Having ones own music is double the enhancement gain from listening to biaural beats. Hurray for this app A+++++

Landofpar about iBrainWave SE - Binaural Beats and White Noise