I have tested your command and it works exactly as expected for me, based on what James mentioned earlier about WMC using the system volume.
What happens for me with your command is that when music is playing in WMC the command mutes the (system) volume entirely, so the music is muted and the TTS is also muted. At the end of the command the volume is unmuted and I can hear my music again.
To test that the command is working, I added an OSD.ShowText to the TTS, and when the volume is muted I can still see this message.
For this reason, James made various suggestions above about alternative options apart from using mute. In general, I know he has recommended to other users that it's best when TTS uses a different audio output from media players (for example, see his post here:
http://voxcommando.com/forum/index.php?topic=1280.msg11054;topicseen#msg11054).
WMC's functionality is generally quite limited compared to other media players, so there may not be a lot of VC users with experience getting around its quirks.
If the command is working for you as I described above, then it is technically "working". It's just not doing what you would like because of the limitation of WMC.
If it's *not* functioning as above, one key question is whether you have WMC set up properly with VC. As James asked previously: do other WMC commands work for you in VoxCommando? That is, have you installed the VMC Controller plugin for WMC, as per the instructions on the VoxCommando wiki? (
http://voxcommando.com/mediawiki/index.php?title=Installation_WMC)
Edit: I forgot to say that I tried James's suggestion earlier in this thread of using a 'pause'/'play' (playrate pause, playrate play) instead of mute, since I am using a laptop and don't have different audio output options. This works, but isn't perfect because play/pause turns out to be a toggle in WMC, not a genuine play or pause action. This means that if music is playing when you issue your Greet Computer command, the song will pause, you get your appropriate tts, then the music plays again exactly as desired. However, if WMC is running but a song is not currently playing, this action will cause a queued track to *start* playing, even if it wasn't before. You may not mind that. If so, that may be the easiest compromise solution.