PC speaker

I've been reading about outputting PCM audio through the internal PC speaker using "Pulse-width modulation". If I understand correctly, this is acheived by retracting the speaker cone before it has a chance to fully extend. My question is now this: would it be possible, by spending all CPU resources on this task, to keep the speaker cone in its current mid-extension position, by rapidly (as fast as the CPU will allow) toggling the current to it?

>>14
Thank you very much for explaining why this technique works, but now I'm wondering if I have misunderstood how the speaker works on a physical level.