Stopping a looping source when an envelope cycle has ended

Hi all!

I just recently started doing some (almost) serious work with Web Audio,
and I'm glad to find that the API and the implementations are moving along
nicely!

One of the things I have not been able to find a nice solution to yet,
though, is a situation that leaks memory and CPU cycles... (I'm sure
there's a solution that I have missed)

I'm playing an AudioBuffer using a looping AudioBufferSourceNode, followed
by a GainNode that acts as an envelope modulator.

Now, one AudioBufferSourceNode + GainNode is created and start():ed for
each note that I play, and all JS references to the nodes are dropped.
Eventually the GainNode will reach zero (when the envelope cycle has
ended), but as far as I can tell, the AudioBufferSourceNode will continue
sampling and eat CPU cycles.

I think that this is correct behavior (the AudioBufferSourceNode has the
playing state set, so it will not be GC:ed), although there seems to be a
difference between Blink & Gecko w.r.t how much CPU is consumed by all the
silent nodes.

Question: What is the best method for stopping / disconnecting a looping
source node at a predefined AudioContext time (i.e. when the GainNode has
finished all the automation events)? I would like to avoid keeping track of
all the active nodes myself (e.g. array of active source nodes + polling &
checking against currentTime).

/Marcus