[old laptop] Stuttering audio when sequencer is running

Tried on a Dell Lattitude D630 with Win7, Intel Core2 Duo, T7250, 2GHz with 4GB RAM.

Let's see if we can figure out by profiling on a modern machine what stands out during playback. My guess is something changed in v0.9.0.17 (The Great Rewrite), but let's verify this performance cutoff before jumping to conclusions.