This feature seems really helpful!
I am considering inviting guests to voice chat (VC) with me while I am gaming (the VC audio will also be on the stream), but I am hesitant because I can't avoid the guests hearing their voice twice from theirselves and the stream. This kind of "echo" makes it difficult to continue speaking, so I want to give them a option to listen to streamed audio without VC.
I believe this is an important feature that it deserves to be charged for. I could not be happier if you would consider implementing it!

I want to add a way for the viewer to manage the various audio tracks, each viewer can customize it as he prefers, in order to hear everything well

Integrate the microphone and background music of a streamer as two distinct input/output channels that can enable viewers to individually adjust the volume levels of each channel according to their preferences. By providing this feature, viewers who enjoy higher background music levels can select accordingly, while others who prefer no background music at all may mute the background music volume. This implementation can result in increased satisfaction among viewers, and alleviate the need for the streamer to constantly adjust background music levels, thereby increasing overall efficiency.

I stream with community sound effects using bot commands. Some people like these, some people don't. I have them set to channel 6 and do not save them to my VODs. I would like my viewers to have the ability to mute on a channel by channel basis on the live stream as well, so everyone can have the best of all worlds.

We can already stream content in this manner, please allow viewers to also control the volume of the different channels on their end.

A streamer has the possibility to set his microphone and his music to 2 audio tracks as is already done, but in the stream itself you only have the option of making the entire stream loud or quiet, a good option here would be to play the music separately turn it down OR just want to listen to the music and turn the streamer down.

example:

You set your Spotify playlist (or local music) & your microphone in OBS. The viewer on Twitch now has another speaker icon when hovering over the speaker icon with the mouse. If he makes the first loudspeaker symbol quiet, only the microphone of the streamer (& potentially the game sound or something) is turned down but the separate music remains loud. The same with the second loudspeaker symbol, only the music is turned down and the streamer remains loud. Of course, if the viewer presses the loudspeaker symbol, both will continue to be muted. The advantage of this would be that the viewer can listen to his music himself and is not "forced" to listen to the music from the streamer.

Example of how it could look like in a stream: https://imgur.com/a/phSdWuI
(not me but i have permission to use this scene/picture, i just edited the second volume thing) (ps: yes ik that the last button is from a plugin and can be ignored.. xD)

Thanks for reading

Love the idea, has Twitch moved forward with it since it being mentioned here for five and a half years?

When can we see this available?
This actually describes the feature I need!

This was requested initially at Nov 5, 2016

but the feature is already half way there since we can have VOD tracks already...

Great idea!

Option for viewers to be able to select to view the live stream with only the VOD track layers configured previously by the streamer.

The VOD track can already be adjusted in OBS by the streamer for the VOD.
We need this same feature but adjusted for a near real-time playback.
If configured properly by the streamer, viewers can select only listen to the game audio and not have to hear the streamer yelling their lungs out, Text-To-Speech, background music, alerts, etc..

As someone who almost always has multiple streams open I actively interact with, this would be the BEST thing Twitch could ever do for me as a viewer. Listening to multiple people talk is not a problem, but if they all play music it becomes a problem.

OBS already allows to stream and record multiple audio tracks. Any media player with audio track selection lets a user switch between them.

Currently Twitch merges those tracks, supposedly at their ingest or transcoding, servers, making it impossible for users or extensions to balance the audio of the individual tracks.

I am aware this is a high-risk feature request, because users WILL complain about the mic being muted when it was them muting the mic on their end, or the music being too loud, when they turned it up on their end.

This means there is a lot more work to this than simply retaining the audio tracks and updating the player to support more than one volume slider. A lot of usability testing would have to be put into this, testing e.g. if putting all track levels at the same level in the client whenever a stream starts would make it acceptable to prevent false accusations of the streamer having messed up VS the annoyance of users to have to change the settings to their preferred balance every stream.

I was thinking of making an extension which would allow viewers to at least switch between the live stream and VOD audio tracks when they watch a stream, because of how common it has become to have the VOD not include music.

But it appears there is no official endpoint available for developers to get the VOD audio track and get it with a latency/delay matching the live stream.

100% agree, we need this asap. At least 2 volume options, one for background music from whatever source (you would just add a Spotify app for example) and another one for the rest of the stream audio like its now. Instead of one "speaker" to modify whole stream volume we would have additional "speaker" to adjust music volume and thats all. Simple as that. Life changing feature - you like the streamer but dont like his music? Just mute it and watch the stream and wait for your own song or play it on your own

Echoing others that have stated that the main benefit for me with this feature is that I would be able to watch a streamer while playing a game, without their game audio interrupting my game audio.

You need to create an option so that the user can
for yourself, turn off the music that the streamer listens to

If we can't get muteable music soon, I am fricken done with twitch. Especially streams that accept audience suggested music. The streamer has it muted why can't I?

Please add a feature that allows the viewer to mute the chosen music by streamer/audience. I understand the concept of taking bits or donos for song requests, but it ruins the stream for a lot of people. I also understand the intention of a streamer personalizing their community/stream with their own music. However, we don't require a DJ whilst viewing most content on twitch. Thank You.

This would be good. Being able to adjust the volume of the streamer microphone and then-all-other-audio on two separate volume bars that the individual viewer can adjust.

This would be super easy to implement as the RTMP protocol that Twitch uses already supports multiple audio channels. But it would also be more expensive for Twitch to transcode/distribute the additional audio channels. I'd love to see this feature for a few more reasons:

1. Surround sound (would be even cooler if Twitch did the downmix from surround to stereo)
2. Multiple languages. You could watch one stream and choose which language you want to watch, would be nice for audio description for vision impaired viewers too.

This is an amazing idea. I always listen to my own music and would love to turn off streamer music.

I like to play games while watching, but I often have to stop as the audio interrupts my game. If I could choose to mix it differently, that would be awesome, nearly as good as having a streaming service on another screen/tv while playing games

Allow viewers to listen in VOD audio mode during a livestream. Let the viewer toggle off the 2nd audio channel that has music.

I watch a streamer that has a lot of music on during his stream, but he has it set so the music isn't recorded in the VODs. Sometimes I would like to be able to watch the stream live without the music (like in the VODs). That way it is less distracting if I'm trying to multi-task or I can play my own music and still watch. Please provide the option to allow me as a viewer the option to toggle into VOD audio mode, or toggle off/on individual audio channels when multiple channels are provided by the streamer for a live stream.