you read two songs of different lengths with two different sample frequency. You convolve them, which is going to give you a result that one fewer samples than the sum of the two lengths; for example conv(4 samples, 9 samples) would result in 4+9-1 = 12 samples.
What time is each of the output samples if the inputs were different frequency?
You then assume that the result has exactly 11 samples, times 0:10. But it is not.
You need to reconsider this process.
Also I recommend reading the options for conv() and thinking about whether one of them is appropriate.
convolution of signals is effectively using one of the signals as a filter on the other signal, where each additional element of the second signal acts like a further time delay. The second signal is roughly deciding how much echo to add to the first signal, and remember that the adding echo makes a signal longer.
