1.) When a music trank is so good, it gives the listener an empowered feeling.
2.) When hearing something gives the listener an orgasm.
Mitsuda's "Proto Merkabah" gives me a soundgasm. So does Emily Bindiger's voice.
Elly had a soundgasm every time she heard a cat meow.
n: The shudders, wide-eyed look, frantic little astounded noises, and eventual amazed torpor that accompanies the listening to an amazing song, usually ending in the person having a glassy-eyed look and acting in the exhausted, drained manner of someone who just had a huge orgasm.
v: To exhibit the behaviors or characteristics that define the act of having a soundgasm.
Oh my lord, I was listening to my friend's MP3 player and she caught me having a soundgasm to the new rock she has on there. I was so embarassed. =]