This demonstrates a linear interpolation formula for achieving a weighted balance of two signals. It has the exact same effect as the previous mixing example, but uses a more efficient formula, requiring one fewer multiplication per sample.

We want a blend (mix) of two sounds, and we specify the balance between the two as a value from 0 to 1, where a balance value of 0 means we get only the first sound, a balance value of 1 means we get only the second sound, and 0.5 means we get an equal mix of the two sounds.

The way we calculate this is
y[n] = x₁[n]+balance(x₂[n]-x₁[n])
where x1 and x2 are the two signal values and balance is the weighting value described above.

mix2~.maxpat

The two audio signals come in the first two inlets, and the balance value comes in the right inlet. The argument #1 will be replaced by whatever is typed in as the object’s first argument when it’s created in the parent patch. This patch subtracts the sound coming in the first inlet from the sound coming in the second inlet, multiplies the result by balance and adds that result to the first sound.

A linear signal from 0 to 1 or from 1 to 0 coming in the right inlet will make a smooth linear crossfade between the two audio signals.