From the test results it becomes clear, that asynchronous programming can help to increase the performance in LAME.

When encoding single files the growth rate depends on the chosen compression method. Here CBR comes off worst because of too strong dependencies while the VBR methods are reaching about double speed.
The best results are achieved with 3 threads. With 4 threads a trip which results from the increasing idleness of single threads occurs.

When encoding several files, fpMP3 scales with an efficiency of about 90%, achieving a very good CPU utilization. With the fact that up to 8 files (4x WAV, 4x MP3) are processed in parallel the achieved efficiency can be uprated.