In the past I have practiced a form of psychotherapy know as EMDR. Practicing EMDR involves alternating bilateral stimuli, whether is visual (provoking eye movements), tactile (with tapping, or buzzers in each hand), or auditory.
I had a little box, called a Tac/AudioScan which had buzzers for tactile stimulation and headphones for audio stimulation.
In December of 2019, I was considering doing EMDR with a patient, and found that my Tac/AudioScan was no longer working. A replacement wasn’t cheap, but I realized I could make a web app for the sound.
You can try it here; click on “Instructions” if it is not self-explanatory.