hearing someone on a c.d. or on myspace music sample different from hearing them

the reason i ask this is because people would tell me that they have never heard me play although they have heard me on cd or on mp3 files.is playing live all that much different?
Lolz! You already posted this!
Strange, It seems like a character mutation, Though I have all the means, of bringing you fuckers down, I can't make myself, To destroy upon command, Somehow forgiveness, lets the evil make a loss - Danger Mouse/Sparklehorse/Wayne Coyne
That's not even a sentence, let alone a question. Do you speak English?