FX not being applied correctly when using :tech_saws synth?

[ethancrawford]

I have observed strange behaviour when applying FX to the :tech_saws synth. See the below example:

live_loop :test do
  #with_fx :reverb, room: 1 do
  with_fx :rlpf, cutoff: 60, mix: 1 do
    synth :tech_saws, note: :c4, sustain: 4, release: 0
  end
  #end
  sleep 4
end

Running the above as-is seems to play the synth as if the :rlpf FX has no effect the first time round the loop. All subsequent iterations seem to have rlpf applied.

Similarly, if I run the above with the :reverb FX uncommented, I also get some unexpected results. The rlpf seems to be applied immediately, but there are gaps near the end of each loop iteration where the synth seems to be unfiltered.

This happens both with v3.0.1 on Mac, and the latest Windows beta 5, so it might not be a new problem.

[ethancrawford]

This behaviour is also noticeable if you wrap the :tech_saws synth with different FX. (Replace the :rlpf with :vowel for example)

[samaaron]

How strange! I can confirm that I can reproduce this issue.

For additional context, this appears to have nothing to do with live_loops. The following code also exhibits broken behaviour:

with_fx :rlpf, cutoff: 60, mix: 1 do
  synth :tech_saws, note: :c4, sustain: 1, release: 0
end

sleep 1

with_fx :rlpf, cutoff: 60, mix: 1 do
  synth :tech_saws, note: :c4, sustain: 1, release: 0
end

[hajookim]

@krinsang and I noticed that if you include "play 0, amp 0" or any other note before the tech_saws, this problem doesn't happen. What could be causing this? Maybe due to a mishandling of threads when creating the initial osc packets where fxnodes are not being loaded properly?
Correct me if our understanding of the code is wrong so that we can pivot and try to look elsewhere.
Thanks @samaaron

[windo]

Hoover has the same behaviour.