The best way to understand SEND and RETURN Levels for an effect like Reverb is to give an analogy of how Reverberation Chambers actually work. Back in the day (my stories of engineering always start "back in the day", as I was a full time recording engineer in the late 1970's).

I was doing a session at New York's Power Station, which had a live reverberation chamber - the five story stairwell in the building - at each landing there was a microphone and a speaker cabinet... you could send signal to the speaker on level 5 while turning on the microphone on level 1 for maximum reverberation. Signal sent to that speaker would reverberate in the stairwell and be pickup several floors later and returned to the console.

So on each channel of the mixer you had a SEND amount which took a portion of that channel's signal and sent it to speaker on level 5. At the board a Reverb Chamber RETURN mixed the composite signal back to the main L/R OUTPUT. So when you went to level 5 what you hear was each SEND - so there was the snare drum, a bit of the tom mics, the vocals, the keyboards, etc. by the time the signal reached level 1 it had bounced off of 5 levels of walls, stairs and ceiling and was plenty reverberant.

The returned signal was a composite of all those instruments and was mixed back to the main L/R signal.

Reverb is subjective - means you do it to taste. So you send enough to cause the reverb chamber to reverberate... you return enough to balance against the DRY signal (the signal that normally travels through all channels to the main L/R Outputs, without reverb).

You send enough so the reverb chamber responds, you return enough to balance against the dry (normal signal) it is all to taste - don't over think it.

The reason the story is so funny is, we'd normally be in the studio in the wee small hours of the morning, (best rates, best time to work)... but there was this crazy noise we were getting - we soloed the return and sure enough it was in the reverb chamber return... come to find out the maintenance crew was vacuuming the stairwell... almost ruined the mixdown! 🙂

So in your ES, the Dry signal from each channel is typically left at 127 - that is the signal that travels from each channel and contributes to the final stereo output.
The SEND Amount per Channel is the relative amount you want to place on each PART you decide needs reverb. The RETURN is always a composite signal (it includes all the instruments send in, now "wet" (dipped) in reverb, if you will). It is always a combined signal and you mix it to your taste with the DRY signal. How much reverb is always a matter of taste.

The amount of SNARE reverb to VOCAL reverb is determined by the SEND AMOUNT on each Channel. The RETURN is always just a stereo return and represents all reverberated signals mixed together into a stereo signal that is merged with the overall DRY.

In general, SYSTEM EFFECTs like reverb are not recorded to the individual Tracks when multi-tracking - they are added and mixed to the final stereo signal. Reverb represents the overall environment that all the musical instruments are playing within - it's the room where they are all playing. The reverb helps the listener discern distance from each player.

Thanks Phil....For my workflow writing/arranging songs..I record-in sequencer / multi-tracking in pattern convert to song and then mute and play live the lead / melody tracks. I am at the point of creating the right sound stage to send thru L & R powered speakers which is my sound system for my ES. In other words, I think I am at the final stereo output / mix down phase of my song. Am I thinking right / right use of such effects as reverb and chorus in the above workflow?

In your explanation, did I understand than the RETURN signal is always 100% wet? And, If I SEND 0 to the effects processor, then, by definition, the RETURN would remain silent even if I set RETURN to 127? (Unless of course, there is a vacuum cleaner in the hall). The parameter sent and returned is only the volume of the signal (dry in and wet back), correct? And when I increase send levels thru the control knobs, I am "increasing" the amount of reverb, meaning I am simply increasing the volume of the dry signal which causes more vibrations / reverb that I will hear returned / mixed with the original dry signal. The mix of wet and dry gives me what I would call my desired saturation of reverb? On my Motif, aren't I only adjusting send levels for each part to set their individual reverb levels? I don't normally open or adjust a return for each to hear my results? As you say, return is done in the end as a composite of everything send in,,,,,, I just adjust send, by control knobs or screen, to get my desired saturation for each part. I guess its master effects where I adjust overall reverb return for the entire mix near the end of the signal path to stereo mixdown, right? Last reverb question, on the Motif, I don't have the ability nor should I want to use different types of reverb on different tracks within the same mix, correct? Only the volume - wet/dry mix levels.

If I SEND 0 to the effects processor, then, by definition, the RETURN would remain silent even if I set RETURN to 127?

Correct.

When you increase a Part's Reverb Send you are literally creating a branch off of the main flow which represents the amount of Reverb you want to apply to a sound relative to others you are sending.

No Send into the Reverb chamber, no return. There are many Sends into the chamber (each channel has a Send) but only one level for return. If you isolated the RETURN, it would sound like a ghostly image of every sound you sent in. Thinner, and slightly delayed, with a long retreat. A composite ghostly sound.

Effects are very subjective. I was taught: know the rules (which is, know why something is done a certain way) this way when you break a rule its because you know you want to, not because think you're a rebel or worse.

Reverb became a necessary evil, if you will, when close miking became a studio technique. Placing a microphone inches from a vocalist does allow us greater isolation from other sources, but the tradeoff is by being unnaturally close, the listener's perception is it doesn't sound normal. Reverb gives the listener a sense of distance from the sound source. Naturally, sound bounces off of the wall and ceiling and floor in an acoustic listening environment, we depend on that for recognizing and locating sound sources. All musical instruments in any ensemble are in the same room when performing, so our expectation of the resulting sound is based on this... If one thing sounds like it is coming from a different space, it would be strange, like say you're in a club listening to a band, and suddenly, from outside you hear a saxophone coming through an open window, it would be immediately identifiable as coming from somewheres else! Out of place even... The synthesizer effects are setup to resemble a recording studio with patchable effects (insert effects) and send/return effects (rev/cho System effects).

So multiple reverbs, not a natural situation... Doesn't mean you can't or shouldn't do it, you most certainly can use multiple Reverb chambers, (reverbs are available as Insert Effect Types) so you could make each instrument sound like its in a different room. I'm just saying that's what it will sound like. So if you would like to create the illusion that a sound is coming from a different spatial setting, you can.