# What happens if an harmonic in a band-limited signal at Nyquist frequency is added to a 90 degrees out-of-phase replica of it?

I'm interested about aliasing in digital audio and I wonder if aliasing can be produced by simple mixing of band-limited signals. As I know a band limited signal can contain frequencies up to sample rate/2 frequency, the so-called Nyquist frequency. Is this right?
If that is so, what will happen if an harmonic in a band-limited signal at Nyquist frequency is added to a 90 degrees out-of-phase replica of it? Will this create an harmonic with double frequency and could such an addition create aliasing?

• Possible duplicate of Can addition of two band limited signals create aliasing? – MBaz Mar 26 '18 at 15:42
• How is this question different from your previous one on the same topic? – MBaz Mar 26 '18 at 15:42
• @MBaz The other one does not address this question and I have already selected it as a correct answer. I tried to ask for this in a comment but got advised by the person who answered my other question to make a new one – user17127 Mar 26 '18 at 15:45
• BTW, recall that Nyquist requires signals to be below $f_s/2$. Harmonics at exacly the Nyquist frequency alias to DC. – MBaz Mar 26 '18 at 15:50