diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2db5982..5bdab1f0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Adds a function to write a `Source` to a `wav` file, see `output_to_wav`.
 - Output audio stream buffer size can now be adjusted.
+- A `ChannelRouterSource` that can mix, re-order and extract channels from a 
+  multi-channel source.
+    - Several `Source` trait helper functions including `extract_channel`, 
+      `extract_channels`, `mono`, `mono_to_stereo`, and `downmix_51`.
+    - A `ChannelRouterController` type to modify the `ChannelRouterSource` 
+      across thread boundaries.
 - Sources for directly generating square waves, triangle waves, square waves, and
   sawtooths have been added.
 - An interface for defining `SignalGenerator` patterns with an `fn`, see
diff --git a/Cargo.toml b/Cargo.toml
index 4e756567..b529bfce 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -88,6 +88,10 @@ required-features = ["symphonia-isomp4", "symphonia-aac"]
 name = "noise_generator"
 required-features = ["noise"]
 
+[[example]]
+name = "channel_routing"
+
 [[example]]
 name = "into_file"
 required-features = ["wav", "mp3"]
+
diff --git a/examples/channel_routing.rs b/examples/channel_routing.rs
new file mode 100644
index 00000000..a1624c4f
--- /dev/null
+++ b/examples/channel_routing.rs
@@ -0,0 +1,45 @@
+//! Channel router example
+
+use std::io::Read;
+use std::{error::Error, io};
+
+fn main() -> Result<(), Box<dyn Error>> {
+    use rodio::source::{Function, SignalGenerator, Source};
+
+    let stream_handle = rodio::OutputStreamBuilder::open_default_stream()?;
+
+    let sample_rate: u32 = 48000;
+
+    let (controller, router) = SignalGenerator::new(sample_rate, 440.0, Function::Triangle)
+        .amplify(0.1)
+        .channel_router(2, &vec![]);
+
+    println!("Control left and right levels separately:");
+    println!("q: left+\na: left-\nw: right+\ns: right-\nx: quit");
+
+    stream_handle.mixer().add(router);
+
+    let (mut left_level, mut right_level) = (0.5f32, 0.5f32);
+    controller.set_map(&vec![(0, 0, left_level), (0, 1, right_level)])?;
+    println!("Left: {left_level:.04}, Right: {right_level:.04}");
+
+    let bytes = io::stdin().bytes();
+    for chr in bytes {
+        match chr.unwrap() {
+            b'q' => left_level += 0.1,
+            b'a' => left_level -= 0.1,
+            b'w' => right_level += 0.1,
+            b's' => right_level -= 0.1,
+            b'x' => break,
+            b'\n' => {
+                left_level = left_level.clamp(0.0, 1.0);
+                right_level = right_level.clamp(0.0, 1.0);
+                controller.set_map(&vec![(0, 0, left_level), (0, 1, right_level)])?;
+                println!("Left: {left_level:.04}, Right: {right_level:.04}");
+            }
+            _ => continue,
+        }
+    }
+
+    Ok(())
+}
diff --git a/src/mixer.rs b/src/mixer.rs
index b1e58f42..c0c5d7d4 100644
--- a/src/mixer.rs
+++ b/src/mixer.rs
@@ -7,7 +7,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
-/// Builds a new mixer.
+/// Builds a new mixer that sums corresponding channels from incoming streams.
 ///
 /// You can choose the characteristics of the output thanks to this constructor. All the sounds
 /// added to the mixer will be converted to these values.
@@ -116,7 +116,7 @@ where
         // let mut encounterd_err = None;
         //
         // for source in &mut self.current_sources {
-        //     let pos = /* source.playback_pos() */ todo!();
+        //     let pos = /* source.playback_pos() */
         //     if let Err(e) = source.try_seek(pos) {
         //         encounterd_err = Some(e);
         //         break;
diff --git a/src/source/channel_router.rs b/src/source/channel_router.rs
new file mode 100644
index 00000000..df3eebf3
--- /dev/null
+++ b/src/source/channel_router.rs
@@ -0,0 +1,312 @@
+// Channel router types and implementation.
+
+use crate::{ChannelCount, Sample, Source};
+use dasp_sample::Sample as DaspSample;
+use std::fmt::{Debug, Formatter};
+use std::{
+    error::Error,
+    fmt,
+    sync::mpsc::{channel, Receiver, Sender},
+};
+
+/// Weighted connection between an input and an output channel.
+/// (source_channel, target_channel, gain)
+// Alternatively this can be a struct but map construction becomes more verbose.
+pub type ChannelLink = (ChannelCount, ChannelCount, f32);
+
+/// An input channels to output channels mapping.
+pub type ChannelMap = Vec<ChannelLink>;
+
+/// Function that builds a [`ChannelMixer`] object.
+/// The new `ChannelMixer` will read samples from `input` and will mix and map them according
+/// to `channel_mappings` into its output samples.
+pub fn channel_mixer<I>(
+    input: I,
+    out_channels_count: u16,
+    channel_map: &ChannelMap,
+) -> (ChannelMixer, ChannelMixerSource<I>)
+where
+    I: Source,
+    I::Item: Sample,
+{
+    let (tx, rx) = channel();
+    let controller = ChannelMixer {
+        sender: tx,
+        out_channels_count,
+    };
+    let source = ChannelMixerSource {
+        input,
+        channel_map: vec![],
+        // this will cause the input buffer to fill on first call to next()
+        current_out_channel: out_channels_count,
+        out_channel_count: out_channels_count,
+        // I::Item::zero_value() zero value is not 0 for some sample types,
+        // so have to use an option.
+        output_frame: vec![None; out_channels_count.into()],
+        receiver: rx,
+    };
+    // TODO Return an error here? Requires to change API. Alternatively,
+    //      map can be set separately, or this can panic.
+    controller
+        .set_map(channel_map)
+        .expect("set channel mixer map");
+
+    (controller, source)
+}
+
+/// `ChannelRouterController::map()` returns this error if the router source has been dropped.
+#[derive(Debug, Eq, PartialEq)]
+pub enum ChannelMixerError {
+    ConfigError,
+    SendError,
+}
+
+impl fmt::Display for ChannelMixerError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "<ChannelMixerError>")
+    }
+}
+
+impl Error for ChannelMixerError {}
+
+/// A controller type that sends gain updates to a corresponding [`ChannelMixerSource`].
+#[derive(Debug, Clone)]
+pub struct ChannelMixer {
+    sender: Sender<ChannelMap>,
+    out_channels_count: ChannelCount,
+}
+
+impl ChannelMixer {
+    /// Set or update the gain setting for a channel mapping.
+    pub fn set_map(&self, channel_map: &ChannelMap) -> Result<(), ChannelMixerError> {
+        let mut new_map = channel_map.clone();
+        self.prepare_map(&mut new_map)?;
+        self.sender
+            .send(new_map)
+            .map_err(|_| ChannelMixerError::SendError)
+    }
+
+    fn prepare_map(&self, new_channel_map: &mut ChannelMap) -> Result<(), ChannelMixerError> {
+        if !new_channel_map
+            .iter()
+            .all(|(_from, to, _gain)| to < &self.out_channels_count)
+        {
+            return Err(ChannelMixerError::ConfigError);
+        }
+        new_channel_map.retain(|(_from, _to, gain)| *gain != 0.0);
+        new_channel_map.sort_by(|a, b| a.0.cmp(&b.0));
+        Ok(())
+    }
+}
+
+/// A source for extracting, reordering, mixing and duplicating audio between
+/// channels.
+pub struct ChannelMixerSource<I>
+where
+    I: Source,
+    I::Item: Sample,
+{
+    /// Input [`Source`]
+    input: I,
+
+    /// Mapping of input to output channels.
+    channel_map: ChannelMap,
+
+    /// The output channel that [`next()`] will return next.
+    current_out_channel: ChannelCount,
+
+    /// The number of output channels.
+    out_channel_count: ChannelCount,
+
+    /// The current input audio frame.
+    output_frame: Vec<Option<I::Item>>,
+
+    /// Communication channel with the controller.
+    receiver: Receiver<ChannelMap>,
+}
+
+impl<I> Debug for ChannelMixerSource<I>
+where
+    I: Source,
+    I::Item: Sample,
+{
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.debug_struct("ChannelMixerSource")
+            .field("channel_map", &self.channel_map)
+            .field("channel_count", &self.out_channel_count)
+            .field("current_channel", &self.current_out_channel)
+            .finish()
+    }
+}
+
+impl<I> ChannelMixerSource<I>
+where
+    I: Source,
+    I::Item: Sample,
+{
+    /// Destroys this router and returns the underlying source.
+    #[inline]
+    pub fn into_inner(self) -> I {
+        self.input
+    }
+
+    /// Get mutable access to the inner source.
+    #[inline]
+    pub fn inner_mut(&mut self) -> &mut I {
+        &mut self.input
+    }
+}
+
+impl<I> Source for ChannelMixerSource<I>
+where
+    I: Source,
+    I::Item: Sample,
+{
+    #[inline]
+    fn current_span_len(&self) -> Option<usize> {
+        self.input.current_span_len()
+    }
+
+    #[inline]
+    fn channels(&self) -> ChannelCount {
+        self.out_channel_count
+    }
+
+    #[inline]
+    fn sample_rate(&self) -> u32 {
+        self.input.sample_rate()
+    }
+
+    #[inline]
+    fn total_duration(&self) -> Option<std::time::Duration> {
+        self.input.total_duration()
+    }
+}
+
+impl<I> Iterator for ChannelMixerSource<I>
+where
+    I: Source,
+    I::Item: Sample,
+{
+    type Item = I::Item;
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_out_channel >= self.out_channel_count {
+            // An improvement idea: one may want to update the mapping when incoming channel count changes.
+            // TODO This condition is normally false. Use an atomic to speedup polling?
+            if let Some(map_update) = self.receiver.try_iter().last() {
+                self.channel_map = map_update;
+            }
+
+            self.current_out_channel = 0;
+            self.output_frame.fill(None);
+            let input_channels = self.input.channels();
+            let mut link_index = 0;
+            let mut in_channel_count = 0;
+            let input = &mut self.input;
+            for (input_channel, sample) in input.take(input_channels as usize).enumerate() {
+                while link_index < self.channel_map.len() {
+                    let (from_channel, to_channel, weight) = self.channel_map[link_index];
+                    if from_channel > input_channel as ChannelCount {
+                        break;
+                    }
+                    if from_channel == input_channel as ChannelCount {
+                        let amplified = sample.amplify(weight);
+                        let c = &mut self.output_frame[to_channel as usize];
+                        // This could be simpler if samples had a way to get additive zero (0, or 0.0).
+                        *c = Some(c.map_or(amplified, |x| x.saturating_add(amplified)));
+                    }
+                    link_index += 1;
+                }
+                in_channel_count += 1;
+            }
+            if in_channel_count < input_channels {
+                return None;
+            }
+        }
+        let sample = self.output_frame[self.current_out_channel as usize];
+        self.current_out_channel += 1;
+        Some(sample.unwrap_or(I::Item::zero_value()))
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.input.size_hint()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::buffer::SamplesBuffer;
+    use crate::source::channel_router::*;
+
+    #[test]
+    fn test_stereo_to_mono() {
+        let input = SamplesBuffer::new(2, 1, [0u16, 2u16, 4u16, 6u16]);
+        let map = vec![(0, 0, 0.5f32), (1, 0, 0.5f32)];
+
+        let (_, test_source) = channel_mixer(input, 1, &map);
+        let v1: Vec<u16> = test_source.take(4).collect();
+        assert_eq!(v1, [1u16, 5u16]);
+    }
+
+    #[test]
+    fn test_upmix() {
+        let input = SamplesBuffer::new(1, 1, [0i16, -10, 10, 20, -20, -50, -30, 40]);
+        let map = vec![(0, 0, 1.0f32), (0, 1, 0.5f32), (0, 2, 2.0f32)];
+        let (_, test_source) = channel_mixer(input, 3, &map);
+        assert_eq!(test_source.channels(), 3);
+        let v1: Vec<i16> = test_source.take(1000).collect();
+        assert_eq!(v1.len(), 24);
+        assert_eq!(
+            v1,
+            [
+                0i16, 0, 0, -10, -5, -20, 10, 5, 20, 20, 10, 40, -20, -10, -40, -50, -25, -100,
+                -30, -15, -60, 40, 20, 80
+            ]
+        );
+    }
+
+    #[test]
+    fn test_updates() {
+        let input = SamplesBuffer::new(2, 1, [0i16, 0i16, -1i16, -1i16, 1i16, 2i16, -4i16, -3i16]);
+        let mut map = vec![(0, 0, 1.0f32), (1, 0, 1.0f32)];
+        let (controller, mut source) = channel_mixer(input, 1, &map);
+        let v1: Vec<i16> = source.by_ref().take(2).collect();
+        assert_eq!(v1, vec![0i16, -2i16]);
+
+        map[0].2 = 0.0f32;
+        map[1].2 = 2.0f32;
+        assert!(controller.set_map(&map).is_ok());
+
+        let v2: Vec<i16> = source.take(3).collect();
+        assert_eq!(v2, vec![4i16, -6i16]);
+    }
+
+    #[test]
+    fn test_arbitrary_mixing() {
+        let input = SamplesBuffer::new(4, 1, [10i16, 100, 300, 700, 1100, 1300, 1705].repeat(4));
+        // 4 to 3 channels.
+        let map = vec![
+            // Intentionally left 1 without mapping to test the case.
+            (2, 0, 1.0f32),
+            (3, 0, 0.1f32),
+            (3, 1, 0.3f32),
+            (0, 1, 0.7f32),
+            (0, 2, 0.6f32),
+            // For better diagnostics this should be rejected, currently it is ignored.
+            (17, 0, 321.5f32),
+        ];
+        let (_controller, mut source) = channel_mixer(input, 3, &map);
+        let v1: Vec<i16> = source.by_ref().collect();
+        assert_eq!(v1.len(), 21);
+        assert_eq!(
+            v1,
+            vec![
+                370i16, 217, 6, 1706, 773, 660, 810, 400, 60, 20, 940, 780, 1230, 600, 180, 130,
+                1283, 1023, 1470, 1001, 420
+            ]
+        );
+    }
+}
diff --git a/src/source/mod.rs b/src/source/mod.rs
index 605057e8..0fbcc0e0 100644
--- a/src/source/mod.rs
+++ b/src/source/mod.rs
@@ -3,14 +3,11 @@
 use core::fmt;
 use core::time::Duration;
 
-use crate::common::{ChannelCount, SampleRate};
-use crate::Sample;
-use dasp_sample::FromSample;
-
 pub use self::agc::AutomaticGainControl;
 pub use self::amplify::Amplify;
 pub use self::blt::BltFilter;
 pub use self::buffered::Buffered;
+pub use self::channel_router::{ChannelMap, ChannelMixer, ChannelMixerSource};
 pub use self::channel_volume::ChannelVolume;
 pub use self::chirp::{chirp, Chirp};
 pub use self::crossfade::Crossfade;
@@ -42,11 +39,15 @@ pub use self::take::TakeDuration;
 pub use self::triangle::TriangleWave;
 pub use self::uniform::UniformSourceIterator;
 pub use self::zero::Zero;
+use crate::common::{ChannelCount, SampleRate};
+use crate::Sample;
+use dasp_sample::FromSample;
 
 mod agc;
 mod amplify;
 mod blt;
 mod buffered;
+mod channel_router;
 mod channel_volume;
 mod chirp;
 mod crossfade;
@@ -346,6 +347,103 @@ where
         )
     }
 
+    /// Creates a [`ChannelMixerSource`] that can mix input channels together and
+    /// assign them to new channels.
+    #[inline]
+    fn channel_router(
+        self,
+        channel_count: u16,
+        channel_map: &ChannelMap,
+    ) -> (ChannelMixer, ChannelMixerSource<Self>)
+    where
+        Self: Sized,
+    {
+        channel_router::channel_mixer(self, channel_count, channel_map)
+    }
+
+    /// Creates a one-channel output [`ChannelMixerSource`] that extracts the channel `channel` from
+    /// this sound.
+    #[inline]
+    fn extract_channel(self, channel: u16) -> ChannelMixerSource<Self>
+    where
+        Self: Sized,
+    {
+        self.extract_channels(vec![channel])
+    }
+
+    /// Creates a [`ChannelMixerSource`] that reorders this sound's channels according to the order of
+    /// the channels in the `channels` parameter.
+    ///
+    /// # Panics
+    ///
+    /// - length of `channels` exceeds `u16::MAX`.
+    #[inline]
+    fn extract_channels(self, channels: Vec<u16>) -> ChannelMixerSource<Self>
+    where
+        Self: Sized,
+    {
+        assert!(
+            channels.len() < u16::MAX.into(),
+            "`channels` excessive length"
+        );
+        let mut mapping = ChannelMap::new();
+        let output_count = channels.len() as u16;
+        for (output_channel, input_channel) in channels.into_iter().enumerate() {
+            mapping.push((input_channel, output_channel as ChannelCount, 1.0f32));
+        }
+        channel_router::channel_mixer(self, output_count, &mapping).1
+    }
+
+    /// Creates a [`ChannelMixerSource`] that mixes all of the input channels to mono with full gain.
+    #[inline]
+    fn mono(self) -> ChannelMixerSource<Self>
+    where
+        Self: Sized,
+    {
+        let mapping: ChannelMap = (0..self.channels()).map(|oc| (0, oc, 1.0f32)).collect();
+        channel_router::channel_mixer(self, 1, &mapping).1
+    }
+
+    /// Creates a [`ChannelMixerSource`] that splits a mono channel into two stereo channels, at half
+    /// their original gain.
+    ///
+    /// # Panics
+    ///
+    /// - `self.channels()` is not equal to 1
+    #[inline]
+    fn mono_to_stereo(self) -> ChannelMixerSource<Self>
+    where
+        Self: Sized,
+    {
+        let mapping: ChannelMap = vec![(0, 1, 0.5f32), (0, 1, 0.5f32)];
+        channel_router::channel_mixer(self, 2, &mapping).1
+    }
+
+    /// Creates a [`ChannelMixerSource`] that mixes a 5.1 source in SMPTE channel order (L, R, C, Lfe, Ls,
+    /// Rs) into a stereo mix, with gain coefficients per [ITU-BS.775-1](itu_775).
+    ///
+    /// [itu_775]: https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.775-1-199407-S!!PDF-E.pdf
+    ///
+    /// # Panics
+    ///
+    /// - `self.channels()` is not equal to 6
+    #[inline]
+    fn downmix_51(self) -> ChannelMixerSource<Self>
+    where
+        Self: Sized,
+    {
+        let three_db_down = std::f32::consts::FRAC_1_SQRT_2;
+        let mapping: ChannelMap = vec![
+            (0, 0, 1f32),
+            (1, 1, 1f32),
+            (2, 0, three_db_down),
+            (2, 1, three_db_down),
+            (4, 0, three_db_down),
+            (5, 1, three_db_down),
+        ];
+        channel_router::channel_mixer(self, 6, &mapping).1
+    }
+
     /// Mixes this sound fading out with another sound fading in for the given duration.
     ///
     /// Only the crossfaded portion (beginning of self, beginning of other) is returned.