Let me try it one more time.
- The signal strength of your incoming vocalist (channel 7) can never be strong/loud/powerfull enough to be “louder” than your x-channel music mix.
- In the digital domain, there is a ceiling no-one can cross. That is 0dBFs. Hence the reason why people use compressors and limiters to make things louder.
So, inevitably there is a limit to getting things “louder”. (I.e. your vocal track)
The only solution to the problem of “can’t get it any louder” is to make other stuff less loud.
Since the master fader lowers all channels (including the vocal track) you need to find a way to lower the music mix vs. the vocal channel. Either you lower all of your music mix faders by the same amount (messing up the mix) or you route the music mix to a group channel, which will you allow to lower it in volume vs. the vocal track.
HTH
Fredo