Virtual Mixers - Are they right for you?

This question comes from a comment by V. Violett, and the subsequent discussion on the Belly Dance Teaching Facebook Group. VV is currently using iTunes as a share within Zoom, and an external mic coming in via the mini-jack plug on the side of her HP laptop. She is seeking ways to streamline her set-up before classes, and is considering a virtual mixer over a physical mixer for her use-case. Here's my thoughts:

Physical Mixers

What a physical mixer can do:
A physical mixer can combine external sources and help you deliver them as one "package" to your computer, while allowing individual volume and gain controls for each device input. This is great for people who are using an iPod or phone for music, external mics of any kind, etc. It can combine the sources into one "package" and deliver it to whatever program you want very seamlessly.

Where it can fall down is using the Zoom share function for your music, because then you are delivering your mic from outside, but your music from inside the computer, and there is sometimes lag or other issues with sound conflict. Also, there isn't great modular control of all your devices in one place. This means you are controlling your music volume in iTunes, your mic volume on the mixer and...really that didn't gain you anything over what you were inputting externally to begin with before you had a mixer.

I recommend physical mixers to people who have multiple external sources, and want a physical device to be able to move levers/turn knobs to control their volume, gain, and balance easily on the fly.

Virtual Mixers

With a little bit of learning the ins-and-outs, virtual mixers (aka cableless mixer, virtual audio cables,  or mixer software) can be a good solution for many people. Set up correctly, a virtual mixer can take anything which produces sound on your computer (a physical device, an application, whatever) and route them and control them however you like. You can combine or split sound sources in various ways depending on your needs. You can create different combinations tailored to different applications, whether you are using Zoom, Skype, giving a presentation, conducting interviews, livestreaming, creating podcasts...there are lots of use-cases. A really good example of a virtual/cableless mixer is Loopback ($99, Apple & Windows versions available), and is VERY user friendly as it has an easy-to-understand visual interface.

Let's take your example and Loopback. Keep in mind I am on a Mac, so the specifics of the device naming may be different, but should be close enough for anyone on a Windows machine to interpret. Let's say you want your mic and your iTunes music to go into Zoom as one sound "package", and you want to control the volume levels for each on your Loopback virtual mixer to balance them before they get into Zoom.

​INPUTTING MUSIC & YOUR VOICE

You will set up a virtual device, which we can call for this example "ZOOM SOUND IN". You will add two sources from the dropdown list:
1) under Running Applications, you'll add iTunes
2) under AudioDevices, add your mic input (will likely show up as the name of the mic)
(Just ignore the Pass-Thru, that is Loopback's ability to capture sound sources so just leave it there.)

It will automatically assign these to Channel 1 & 2. You don't need to change that for this simple example.

Now in Zoom, set your Microphone to this new virtual device called "ZOOM SOUND IN", which is now capturing both your iTunes and your mic and sending them as one signal.

Within Loopback, there are simple sliders to adjust volume of individual and/or combined sound sources. You can have a friend log in to test the levels, or simply log in alone and record some footage to watch/listen back, and make adjustments as you deem necessary.

HEARING STUDENTS AND YOUR OWN MUSIC

How about getting that sound back out again, for being able to hear your students and your music? Set up a virtual device called "ZOOM SOUND OUT", and again ignore the Pass-Thru device--just leave it alone.
1) set one source as either Running Applications>Zoom.app OR Audio Devices>ZoomAudioDevice*. 
2) set the other as iTunes again
(*In testing, I have not seen any difference between the two for my use cases, so I just use "ZoomAudioDevice" for mine. Let me know if you learn anything about this which contradicts my understanding.)

These will again route through Channels 1 & 2. Now on this one you want to set a Monitor, which is an additional place you want the sound to output. If you are just putting that through your laptop speakers, you can put in "Built in Output". If you have another set of speakers set in your system, that maybe available as an option, but note: this is one place I have a definite gap in my experience/understanding of Loopback's capabilities. If you are using your mini-jack/3.5mm input for a mic, I am not sure what options you have for speaker outputs other than your Built-In Output. You will need to seek out other tutorials for this, and I have a few YouTubers (listed below) I'd recommend checking out.

Finally, go into Zoom and set your Speaker setting to your new virtual device called "ZOOM SOUND OUT" (or whatever you chose to name it). This should now deliver your participant's voices and your iTunes music to the speakers of your choice set in Monitors of your Loopback device.

I hope this works for you. If I have missed anything let me know. I am just learning this software myself.

Here are some great YouTubers to increase your knowledge!
Fei's channel has been an evolving source of great information for streamers, including dance teachers:
https://www.youtube.com/channel/UCm85VUgZyONBCie0rZIrguw

And I have to give a huge shoutout to the super adorable Dana and her video, which isn't sound-specific, but is an excellent checklist of how to make your dance classes online better.
youtu.be/rW3U2Fv2CY8