plincoln
So I don't see the point of the channel/bank/instrument fields for soft synths - are they in fact pointless for soft synths, somehow the soft synth does it all in the background, doesn't need me to do any filling in per my experience. And if so then it seems that I might have to only fill in the channel/bank/instrument fields for some other type of synth - what might that be, a hardware synth that's attached? Some synth that doesn't have a GUI?
You have several questions here, but this seems to be the core of your dilemma.
Also some of the answers are swinging a bit wide because of the wording in your initial post. In particular, you are not looking at the Synth (audio) output.
You are looking at the MIDI track output to the synth input. It's a very important distinction.
I'm going to ignore the synth audio output for now and focus on the MIDI track, as this is where all of your questions are.
The following screenshots illustrate two scenarios.
In the first, channel, bank, and patch(instrument) settings are relevant.
In the second, bank and patch have no bearing.

Here we have TTS-1 inserted into the project. It is a GM2 softsynth, and as such, it does make use of the bank and patch settings. When TTS-1 is inserted, the bank and patch fields populate with drop down menus.
It is also multi-timbral, and this is where the channels Scott refers to are important.
Each of the 16 parts is preset to receive one of the available 16 MIDI channels.
In this example, track 13 is the synth audio output from TTS-1(note the track input).
Now, to the meat of your question.
Tracks 14-16 are MIDI tracks, and each is set to a unique output channel. I have also used the bank and patch settings to specify which instrument will be played in each part.
Track 14 settings:
Output: 5Cakewalk TTS-1(I'll go into the prefix/suffix later).
Channel:
TTS-1 Channel 1Bank: 15488 Preset Normal (bank)0.
Patch:
VibraphoneTrack 15 settings:
Output: 5Cakewalk TTS-1
Channel:
TTS-1 Channel 2Bank: 15488 Preset Normal (bank)0.
Patch:
Tubular BellTrack 16 settings:
Output: 5Cakewalk TTS-1
Channel:
TTS-1 Channel 10Bank: 15360 Preset Rhythm. This is the GM standard drum bank.
Patch:
Power Set Each MIDI track is sending data to the specified instrument part within TTS-1.
So what happens if I do not select any channels?
The controller will determine the channel that receives data (if the input is set to Omni). Most controllers default to channel 1, so only part 1(vibraphone) would play. However, If I set the controller to channel 10, I will get only drums.
If I set the input to Omni, and select the appropriate output channels, all three parts will play when I hit a key.
With me so far?
From what I can see, the EW player is not multi-timbral. You would need a separate instance for each instrument.
With everything left at default settings, you would get sound without selecting a channel, because the default is already channel 1.
The bank and patch settings are not relevant to EW, so these fields are blank. Patch selection is made within the synth GUI. This is typical for the vast majority of soft synths.
Among other things, the EW player is probably not your best choice for trying to understand your question.
OK, on to the second scenario.

Here, we have 2 instances of Sampletank 2 in the project.
Let's look at those prefixes now.
I have 4 soft synths in my synth rack.
Synth 1 is the first instance of Sampletank, so it appears as 1-SampleTank2.x1.
Synth 4 is the second instance, and it appears as 4-SampleTank 2.x2.
The other two only appear once, so there is no iteration suffix.
As in the other example, MIDI tracks 4,5,and 6 have their outputs set to channels 1,2,and 10, respectively.
The channels correspond to the indivual parts in the synth GUI.
Instruments are selected from menus in the synth GUI, so bank and patch are blank, since they are not relevant to this synth.
Channels are important, because like TTS-1, each part is preset to receive on a given channel.
This is really just basic MIDI routing, but it can be confusing at first.
Take a minute to digest all of this.
Hopefully it helps.
post edited by RobertB - 2015/03/25 14:16:41