Note that the only appropriate way to distribute an LFX is as part of a complete audio driver package. Of course, if this is just for experimentation/proof of concept then do whatever you want. Frank Yerrace Microsoft Corporation This posting is provided "AS IS" with no warranties, and confers no rights. From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Tim Roberts Sent: Thursday, June 25, 2009 5:42 PM To: wdmaudiodev@xxxxxxxxxxxxx Subject: [wdmaudiodev] Re: How to filter microphone voice? kevinrich47 wrote: Thank you Tim,What I want is not change voice for single app,but for all application on the machine, I have consider Virtual Audio Cable,But the price is not affordable for me. Oh, come on! There's a free version with some features limited for you to try out, and the full version is only $30. If you have not done audio drivers before, it will save you MONTHS of frustration. If you are working on Vista, you can write a Local Effects Audio Processing Object (LFX APO) to do this. This is a user-mode DLL that lives in the the audio engine process. There is a sample in the WDK in src\audio\sysfx. It's a little bit tricky to get one installed to begin with, but there are documents available to help with that. -- Tim Roberts, timr@xxxxxxxxx<mailto:timr@xxxxxxxxx> Providenza & Boekelheide, Inc.