Error using Horzcat Dimensions

I am trying to write a code that investigates real-time processing of audio signals for the purpose of generating echos. I am getting the horzcat error. If someone can explain to me how to fix my dimensions, that would be greatly appreciated.

[Stephen23]

What size is m ?

Answer 1

[Walter Roberson]

We do not know what m is, but it is not a vector or array with one row, so y is not being initialized to one row as needed by that horzcat.

I recommend that you make y a column vector and change the padding appropriately. column vector would prevent confusion and clashes with the fact that audio data is expected to be one column per channel.