buzzing slowing backing track during vocal overdubbing

Hi- can anybody suggest a remedy for an MP3 backing track that plays fine played alone during playback, but when used as a backing track for a vocal overdub it buzzes, slows down then speeds up, and is un-useable as a backing track. Latency has been corrected, and am using a USB mixer M-audio fast track hooked to a windows computer with Intel core i5 chip. Is it the mixer driver perhaps? Ideas? Thanks- oh, it is using the latest version of audacity.

Your computer is probably getting interrupted by multitasking and there’s not enough remaining processing-power remaining to record & play at the same time. Unfortunately, the operating system is always multitasking even when you’re only running one application and there are various “processes” running the background.

[u]How can I record without small skips (dropouts) or duplications?[/u].

There is a FREE program called [u]LatencyMon[/u] that can help to track-down whatever is eating-up all of your CPU cycles.

And there is a FREE online book about optimizing your computer for audio called [u]Glitch Free[/u]. It’s a short book but it is a book. :frowning: