Instrumental volume decreases when using mon mix dial to increase my voice playback?

Couldn't quite figure out how to word that in the question better lol but I'm fairly new to recording so I'll try to keep it basic I'm using sonar 6 producer edition with a tascam us-122mkII usb interface and a art m4 condenser microphone. I want to be able to hear my own voice in real time in my headphones while I record, I figured it out but the issue is i want the mp3 instrumental playback louder than it is. I have my phones/line out dial maxed out for volume and my mon mix dial needs to be closer to input(to the left) to have my voice nice and loud in my headphones while im recording, but the problem is the more i turn my voice up in my headphones the music gets lower, and if i turn it to the right the music gets louder but i cant hear my voice now during recording. im sorry for the long input but im new to recording and trying to word this my best, if someone could help but take it easy on me lol im learning, thanks so much :)

Sounds like that can help, how do I do that?

thanks man, it worked. Much appreciated. I raised the volume, it didn't go as loud as I would prefer it, but still a major appovement. Thanks :)

Cool. Lower the volume of the vocal you're recordinq and raise the overall output on the TASCAM. Try to balance it out so the music is loud enough and you can hear the vox. The US-122 has some kind of software mixer in which you can adjust those levels, doesn't it?