On GotSound.org we are using wavesurfer.js to play sounds in a browser.
It's works only in modern browsers supporting Web Audio.
MediaElement fallback to support old browsers like Internet Explorer not always works.
You can find more information about browser supported Web Audio API here.
Please, consider to upgrade your browes to one of the following:
Synth lead created on the Minibrute, tweaking the KBD Tracking and LFO rate dials. Was played above the 63 bpm Synth Loop which is also on my selection of freesounds. Enjoy!