diff --git a/CHANGELOG.md b/CHANGELOG.md
index bcb18d30..c20b2af5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- the macro `channel!` now accepts a channel specification that is of the
+  format `factor * (pid, ..) + ...`
 - Python API: dropped top-level Python interface layer
 - Python API: renamed `lumi` to `channel` in PyO3 Python interface. This
   concerns 1) the argument names of `convolute_with_one` and similar functions;
diff --git a/pineappl/src/boc.rs b/pineappl/src/boc.rs
index 1bbfe972..a5fe98b7 100644
--- a/pineappl/src/boc.rs
+++ b/pineappl/src/boc.rs
@@ -571,12 +571,12 @@ impl Channel {
     /// use pineappl::boc::Channel;
     /// use pineappl::channel;
     ///
-    /// let entry = channel![103, 11, 10.0].translate(&|evol_id| match evol_id {
+    /// let entry = channel![10.0 * (103, 11)].translate(&|evol_id| match evol_id {
     ///     103 => vec![(2, 1.0), (-2, -1.0), (1, -1.0), (-1, 1.0)],
     ///     _ => vec![(evol_id, 1.0)],
     /// });
     ///
-    /// assert_eq!(entry, channel![2, 11, 10.0; -2, 11, -10.0; 1, 11, -10.0; -1, 11, 10.0]);
+    /// assert_eq!(entry, channel![10.0 * (2, 11) + -10.0 * (-2, 11) + -10.0 * (1, 11) + 10.0 * (-1, 11)]);
     /// ```
     #[must_use]
     pub fn translate(&self, translator: &dyn Fn(i32) -> Vec<(i32, f64)>) -> Self {
@@ -606,7 +606,7 @@ impl Channel {
     /// use pineappl::channel;
     /// use pineappl::boc::Channel;
     ///
-    /// let entry = channel![4, 4, 1.0; 2, 2, 1.0];
+    /// let entry = channel![1.0 * (4, 4) + 1.0 * (2, 2)];
     ///
     /// assert_eq!(entry.entry(), [(vec![2, 2], 1.0), (vec![4, 4], 1.0)]);
     /// ```
@@ -639,11 +639,11 @@ impl Channel {
     /// ```rust
     /// use pineappl::channel;
     ///
-    /// let ch1 = channel![2, 2, 2.0; 4, 4, 2.0];
-    /// let ch2 = channel![4, 4, 1.0; 2, 2, 1.0];
-    /// let ch3 = channel![3, 4, 1.0; 2, 2, 1.0];
-    /// let ch4 = channel![4, 3, 1.0; 2, 3, 2.0];
-    /// let ch5 = channel![2, 2, 1.0; 4, 4, 2.0];
+    /// let ch1 = channel![2.0 * (2, 2) + 2.0 * (4, 4)];
+    /// let ch2 = channel![1.0 * (4, 4) + 1.0 * (2, 2)];
+    /// let ch3 = channel![1.0 * (3, 4) + 1.0 * (2, 2)];
+    /// let ch4 = channel![1.0 * (4, 3) + 2.0 * (2, 3)];
+    /// let ch5 = channel![1.0 * (2, 2) + 2.0 * (4, 4)];
     ///
     /// // ch1 is ch2 multiplied by two
     /// assert_eq!(ch1.common_factor(&ch2), Some(2.0));
@@ -741,16 +741,21 @@ impl FromStr for Channel {
 /// ```rust
 /// use pineappl::channel;
 ///
-/// let entry1 = channel![2, 2, 1.0; 4, 4, 1.0];
-/// let entry2 = channel![4, 4, 1.0; 2, 2, 1.0];
+/// let entry1 = channel![1.0 * (2, 2) + 1.0 * (4, 4)];
+/// let entry2 = channel![1.0 * (4, 4) + 1.0 * (2, 2)];
 ///
 /// assert_eq!(entry1, entry2);
 /// ```
 #[macro_export]
 macro_rules! channel {
-    // TODO: generalize this to accept an arbitrary number of PIDs
-    ($a:expr, $b:expr, $factor:expr $(; $c:expr, $d:expr, $fac:expr)*) => {
-        $crate::boc::Channel::new(vec![(vec![$a, $b], $factor), $((vec![$c, $d], $fac)),*])
+    ($factor:literal * ($($pids:expr),+) $(+ $more_factors:literal * ($($more_pids:expr),+))*) => {
+        $crate::boc::Channel::new(
+            vec![
+                (vec![$($pids),+], $factor) $(,
+                (vec![$($more_pids),+], $more_factors)
+                )*
+            ]
+        )
     };
 }
 
@@ -965,7 +970,7 @@ mod tests {
     fn channel_from_str() {
         assert_eq!(
             str::parse::<Channel>(" 1   * (  2 , -2) + 2* (4,-4)").unwrap(),
-            channel![2, -2, 1.0; 4, -4, 2.0]
+            channel![1.0 * (2, -2) + 2.0 * (4, -4)]
         );
 
         assert_eq!(
diff --git a/pineappl/src/grid.rs b/pineappl/src/grid.rs
index bcc1f244..b9a5a924 100644
--- a/pineappl/src/grid.rs
+++ b/pineappl/src/grid.rs
@@ -1667,8 +1667,8 @@ mod tests {
         let mut grid = Grid::new(
             PidBasis::Pdg,
             vec![
-                channel![2, 2, 1.0; 4, 4, 1.0],
-                channel![1, 1, 1.0; 3, 3, 1.0],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
             ],
             vec![Order::new(0, 2, 0, 0, 0)],
             vec![0.0, 0.25, 0.5, 0.75, 1.0],
@@ -1690,8 +1690,8 @@ mod tests {
             PidBasis::Pdg,
             vec![
                 // differently ordered than `grid`
-                channel![1, 1, 1.0; 3, 3, 1.0],
-                channel![2, 2, 1.0; 4, 4, 1.0],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
             ],
             vec![Order::new(1, 2, 0, 0, 0), Order::new(1, 2, 0, 1, 0)],
             vec![0.0, 0.25, 0.5, 0.75, 1.0],
@@ -1718,8 +1718,8 @@ mod tests {
         let mut grid = Grid::new(
             PidBasis::Pdg,
             vec![
-                channel![2, 2, 1.0; 4, 4, 1.0],
-                channel![1, 1, 1.0; 3, 3, 1.0],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
             ],
             vec![Order::new(0, 2, 0, 0, 0)],
             vec![0.0, 0.25, 0.5, 0.75, 1.0],
@@ -1740,8 +1740,8 @@ mod tests {
         let mut other = Grid::new(
             PidBasis::Pdg,
             vec![
-                channel![2, 2, 1.0; 4, 4, 1.0],
-                channel![1, 1, 1.0; 3, 3, 1.0],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
             ],
             vec![
                 Order::new(1, 2, 0, 0, 0),
@@ -1777,8 +1777,8 @@ mod tests {
         let mut grid = Grid::new(
             PidBasis::Pdg,
             vec![
-                channel![2, 2, 1.0; 4, 4, 1.0],
-                channel![1, 1, 1.0; 3, 3, 1.0],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
             ],
             vec![Order::new(0, 2, 0, 0, 0)],
             vec![0.0, 0.25, 0.5, 0.75, 1.0],
@@ -1798,7 +1798,10 @@ mod tests {
 
         let mut other = Grid::new(
             PidBasis::Pdg,
-            vec![channel![22, 22, 1.0], channel![2, 2, 1.0; 4, 4, 1.0]],
+            vec![
+                channel![1.0 * (22, 22)],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
+            ],
             vec![Order::new(0, 2, 0, 0, 0)],
             vec![0.0, 0.25, 0.5, 0.75, 1.0],
             vec![Conv::new(ConvType::UnpolPDF, 2212); 2],
@@ -1826,8 +1829,8 @@ mod tests {
         let mut grid = Grid::new(
             PidBasis::Pdg,
             vec![
-                channel![2, 2, 1.0; 4, 4, 1.0],
-                channel![1, 1, 1.0; 3, 3, 1.0],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
             ],
             vec![Order::new(0, 2, 0, 0, 0)],
             vec![0.0, 0.25, 0.5],
@@ -1849,8 +1852,8 @@ mod tests {
             PidBasis::Pdg,
             vec![
                 // channels are differently sorted
-                channel![1, 1, 1.0; 3, 3, 1.0],
-                channel![2, 2, 1.0; 4, 4, 1.0],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
             ],
             vec![Order::new(0, 2, 0, 0, 0)],
             vec![0.5, 0.75, 1.0],
@@ -1878,7 +1881,7 @@ mod tests {
     fn grid_convolutions() {
         let mut grid = Grid::new(
             PidBasis::Pdg,
-            vec![channel![21, 21, 1.0]],
+            vec![channel![1.0 * (21, 21)]],
             vec![Order {
                 alphas: 0,
                 alpha: 0,
@@ -1923,8 +1926,8 @@ mod tests {
         let mut grid = Grid::new(
             PidBasis::Pdg,
             vec![
-                channel![2, 2, 1.0; 4, 4, 1.0],
-                channel![1, 1, 1.0; 3, 3, 1.0],
+                channel![1.0 * (2, 2) + 1.0 * (4, 4)],
+                channel![1.0 * (1, 1) + 1.0 * (3, 3)],
             ],
             vec![Order::new(0, 2, 0, 0, 0)],
             vec![0.0, 0.25, 0.5, 0.75, 1.0],
diff --git a/pineappl/src/pids.rs b/pineappl/src/pids.rs
index 643725f8..e7453857 100644
--- a/pineappl/src/pids.rs
+++ b/pineappl/src/pids.rs
@@ -938,7 +938,7 @@ mod tests {
     #[test]
     fn inverse_inverse_evol() {
         for pid in [-6, -5, -4, -3, -2, -1, 1, 2, 3, 4, 5, 6] {
-            let result = &channel![pid, pid, 1.0]
+            let result = &channel![1.0 * (pid, pid)]
                 .translate(&pdg_mc_pids_to_evol)
                 .translate(&evol_to_pdg_mc_ids);
 
@@ -1031,14 +1031,28 @@ mod tests {
 
     #[test]
     fn translate() {
-        let channel = PidBasis::Evol.translate(PidBasis::Pdg, channel![103, 203, 2.0]);
+        let channel = PidBasis::Evol.translate(PidBasis::Pdg, channel![2.0 * (103, 203)]);
 
         assert_eq!(
             channel,
-            channel![ 2,  2,  2.0;  2, -2, -2.0;  2,  1, -2.0;  2, -1,  2.0;
-                     -2,  2,  2.0; -2, -2, -2.0; -2,  1, -2.0; -2, -1,  2.0;
-                      1,  2, -2.0;  1, -2,  2.0;  1,  1,  2.0;  1, -1, -2.0;
-                     -1,  2, -2.0; -1, -2,  2.0; -1,  1,  2.0; -1, -1, -2.0]
+            channel![
+                2.0 * (2, 2)
+                    + -2.0 * (2, -2)
+                    + -2.0 * (2, 1)
+                    + 2.0 * (2, -1)
+                    + 2.0 * (-2, 2)
+                    + -2.0 * (-2, -2)
+                    + -2.0 * (-2, 1)
+                    + 2.0 * (-2, -1)
+                    + -2.0 * (1, 2)
+                    + 2.0 * (1, -2)
+                    + 2.0 * (1, 1)
+                    + -2.0 * (1, -1)
+                    + -2.0 * (-1, 2)
+                    + 2.0 * (-1, -2)
+                    + 2.0 * (-1, 1)
+                    + -2.0 * (-1, -1)
+            ]
         );
     }
 }
diff --git a/pineappl/tests/drell_yan_lo.rs b/pineappl/tests/drell_yan_lo.rs
index 62e9efaa..aa86a8d9 100644
--- a/pineappl/tests/drell_yan_lo.rs
+++ b/pineappl/tests/drell_yan_lo.rs
@@ -120,15 +120,15 @@ fn hadronic_pspgen(rng: &mut impl Rng, mmin: f64, mmax: f64) -> Psp2to2 {
 fn fill_drell_yan_lo_grid(rng: &mut impl Rng, calls: u32, dynamic: bool, reweight: bool) -> Grid {
     let channels = vec![
         // photons
-        channel![22, 22, 1.0],
+        channel![1.0 * (22, 22)],
         // up-antiup
-        channel![2, -2, 1.0; 4, -4, 1.0],
+        channel![1.0 * (2, -2) + 1.0 * (4, -4)],
         // antiup-up
-        channel![-2, 2, 1.0; -4, 4, 1.0],
+        channel![1.0 * (-2, 2) + 1.0 * (-4, 4)],
         // down-antidown
-        channel![1, -1, 1.0; 3, -3, 1.0; 5, -5, 1.0],
+        channel![1.0 * (1, -1) + 1.0 * (3, -3) + 1.0 * (5, -5)],
         // antidown-down
-        channel![-1, 1, 1.0; -3, 3, 1.0; -5, 5, 1.0],
+        channel![1.0 * (-1, 1) + 1.0 * (-3, 3) + 1.0 * (-5, 5)],
     ];
 
     let orders = vec![
diff --git a/pineappl_cli/src/import/fktable.rs b/pineappl_cli/src/import/fktable.rs
index 1eb67282..6638d650 100644
--- a/pineappl_cli/src/import/fktable.rs
+++ b/pineappl_cli/src/import/fktable.rs
@@ -1,7 +1,7 @@
 use anyhow::{anyhow, Context, Result};
 use flate2::read::GzDecoder;
 use ndarray::s;
-use pineappl::boc::{Channel, Kinematics, Order, ScaleFuncForm, Scales};
+use pineappl::boc::{Kinematics, Order, ScaleFuncForm, Scales};
 use pineappl::channel;
 use pineappl::convolutions::{Conv, ConvType};
 use pineappl::grid::Grid;
@@ -86,14 +86,14 @@ fn read_fktable(reader: impl BufRead) -> Result<Grid> {
                         .iter()
                         .enumerate()
                         .filter(|&(_, &value)| value)
-                        .map(|(index, _)| channel![basis[index / 14], basis[index % 14], 1.0])
+                        .map(|(index, _)| channel![1.0 * (basis[index / 14], basis[index % 14])])
                         .collect()
                 } else {
                     flavor_mask
                         .iter()
                         .enumerate()
                         .filter(|&(_, &value)| value)
-                        .map(|(index, _)| Channel::new(vec![(vec![basis[index]], 1.0)]))
+                        .map(|(index, _)| channel![1.0 * (basis[index])])
                         .collect()
                 };