What seems to be an ordinary task for somebody who has to do with audio recording, I get asked sometimes by listeners. First of all: I use 2 audio interfaces to achieve this. I am aware that there might be "easier" setup forms which only require one single audio interface and some software routing. However, this is the way I managed it. This is not a tutorial about how to do it the simplest or cheapest way. It is just a demonstration of my personal setup for my requirements. Anyway, trying to achieve this with just one audio interface may cause limitations in the use of real time effects (VST/AU) and sending the processed audio in real time through the game. A common issue is also the feedback the audience receives through your channel when they are talking. That is why I seperated audio processing and the actual game input device to two different devices. You may have to use different adapters from chinch to jack and from stereo jack to two mono jacks. Please read the descriptions in the order they are numbered.
How to sing and stream live with an instrumental playback
1) Me personally I like to hold a microphone in the hand while singing. But at the same time I like the sound of a condenser microphone. That is why I chose a handheld condenser microphone like the AKG C5.
2) Connect the microphone via a XLR cable with a (USB) audio interface. Make sure that the interface has low latency and can provide 48V phantom power in case you use a condenser microphone. For me the Focusrite Scarlett Solo 2nd Gen. was the right choice.
3) Additionally to the first USB audio interface, connect another audio interface to your computer, preferably a mixer with 2 seperate stereo line in channels. Watch out that it indeed is capable to send at least 2 seperate stereo channels over USB, instead of just the main mix. Not many low priced mixers can do that. For instance, the Soundcraft Notepad-12FX or Presonus StudioLive AR8 USB mixers are suitable.
4) Connect the analog audio output of the first audio interface with one of the line in stereo channels of the second audio interface / mixer. For this example we choose input stereo channel 5/6.
5) Run at least one DAW / recording software on the computer and select the first audio interface (where the mic is connected) as audio input and ouput device. In this software the magic happens. Create an audio track and put the instrumental file of your song on it. Create another track with the mic as input channel and put insert effects like compressor, EQ and reverb on it. For me Cubase works great. But you might also use a basically free software like Reaper. Instrumentals you can find on YouTube and download them with a Video Downloader as a wav file to import them into the DAW.
6) While singing and hearing the live effects, you should turn off your speakers and sing entirely wearing headphones.
7) Optional: If you want to record your musical mix with voice and seperately the audio of the audience which listens to you (in a game like Comedy Night for instance), start a second DAW software, but this time select the mixer as the audio input device. Create 2 tracks. One track has the 5/6 channel of the mixer as input (your musical mix), and the other track should get the input from the mixer channel 7/8 with which you connected the output of your built in sound card with (see point 8 and 9).
8) Optional: If you want to record your musical mix with voice and seperately the audio of the audience which listens to you (in a game like Comedy Night for instance), connect the output of your built in sound card with a stereo input channel of the mixer. For this mixer we choose input stereo channel 7/8.
9) Since games like Comedy Night choose the default Windows input and output devices, open the Windows audio settings and set the built in output as default output, -and the 5/6 input of the mixer as default input source.
Hear it on YouTube.