Some applications are reporting different stats than Activity Monitor? So here's something I'm curious about:  

When running a full project in Ableton Live (music production), I am (when setting sample rate to the max) getting get drop outs and stuttering. This is as expected and Ableton Live's CPU meter confirms this with values from 80% to 100%. 



However, according to MacOS' own Activity Monitor CPU usage never exceeds 60-70%. How can this discrepancy be?



EDIT: This machine has a 2,5 Ghz Quad-Core
The answer to your question is given in an article from the Knowledge Base of Abelton entitled : CPU meter shows a different value than the Activity Monitor/Task Manager.
Here is the main points :


The value shown on Live's CPU meter differs from Activity Monitor (Mac) or the Task Manager (Windows) since it shows Live's audio processing load but doesn't show Live's overall CPU usage
[...]
Another reason for differing values between Live's CPU meter and the system's CPU meters is that the Activity Monitor and Task Manager normally show 100% per core/CPU. For example, 200% CPU load on the system CPU load meter of a quad-core machine means half of the computer's processing power is in use.


Read the original article for full details.