Can I do this as a send in Reaper? – Hosts & Applications (Sequencers, DAWs, Audio Editors, etc.) Forum

I think it’s possible. But be aware you are dealing with a feedback loop. So good lord turn down the volume of your monitoring system while experimenting with this routing!

1. Your part 1 is on track 1 with fx A. Move fx B on a new track. Let’s call that track, track 2. You bus track 1 with fx A through to track 2 with fx B. So your part 1 is in series processed by fx A + B like before.

Now your part 1 can only be heard through Track 2. On Track 3 is your part 2. On track 4 is your delay fx return.

2. Send signal in parallel from track 2 and 3 to track 4 (delay fx).

3. From track 4 send delay fx output via bus (same bus like the one between track 1 and 2) back to track 2.

Done.