This may have already been discussed to death so forgive me if this is just a repeat:
I use Reaper DAW so this may or may not apply to other DAW's... but I think it does apply to most.
If you want to really see what I'm talking about here, I'd suggest you go get this new Neb skin and use it for your experiments: [url]http://stash.reaper.fm/theme/1382/4VU4U.N2S[/url]
OK... so in Reaper, IF you put Neb directly on a track it gets the signal at a pre fader, and pre pan amount. You can see this in this Neb skin very easily. For example, change the panning of the track and you will hear the change but you will not see the change in the Nebula meters. OK?
Now instead of that method, put the audio file on a different track and send it to the track that has Nebula on it. In the send dialog, set it for Audio 1/2 to 1/2 and MIDI = NONE. Also set the send method to Post Fader-Post Pan. Also set the Master Parent on this sending track to OFF [uncheck the MP box]
Now when you change the fader and\or pan on the sending track you will see those results in the GUI of Nebula. Of course you can then tweak the In and Out further in the Nebula GUI. [start with them at default please]
I have opened a question to the Reaper developers here: [url]http://forum.cockos.com/showthread.php?t=139793[/url]
Perhaps you'd care to join in?
OK... I'll sit quietly now and wait to see what others have to say.
more easy is to use a plugin as the free MonoChannel / StereoChannel made by SleepTimeRecords.
It gives VU meters you can calibrate at whatever you want (like -18 dBFS RMS for most of AlexB's libraries) (don't forget to set the metering to output metering if you want to see the changes ), a trim function to increase or decrease level, and simple mute, phase-invert, high-pass filter and low/mid/treble tone controls.
The stereo version has mid/side possibility and panning as well.
If you need an effective lean-and-mean tool for simple track and mix controls, but want it somewhere placed in your insert-chain, I really recommend this one. There are also volume-trimmers and other stuff in the JS-plugin collection bundled with Reaper.
Also know that you can go to the properties of an audio item (select it and press f2 or use the rightclick menu) and somewhere in the middle is a volume trim + pan control, which you can use to adjust just this single item (which makes it louder/softer before it even hits the first plugin on the track).
Another thing for new Reaper users: Install the free SWS extension if you didn't already (http://sws.mj-s.com/).
A great help (but a bit more for power users) if you're looking for something is the 'action list'. (? key). Every single function that Reaper has (A LOT) is listed here. Some have shortcuts, some have toolbar buttons, some have track controls... but there are a lot of functions that are simply NOT in the UI by default, but they are in the action list. (The SWS extension adds a bunch of stuff here). If you find an action that you think is useful, you can create your own toolbar with a button for it or assign a keyboard shortcut. The filter box is key here to search for stuff .
The SWS extensions adds some RMS functions like 'analyse and display peak RMS and average RMS for selected item', 'normalize by peak RMS', 'normalize by average RMS' and more. I find myself using these a lot in the 'prepare for mixing' stage. When I have a sh*tload of tracks, I often (I know it's not entirely 'right' but I like the results) normalize them all to -19 dBFS RMS, and then I can dump AlexB preamps + consoles on them and know the levels will be alright. Then I start a new project (in a new tab or something) and import the nebulized-files and start setting levels and mixing it.
The SWS functions 'render track to mono bounce (use time selection)' and 'render track to stereo bounce (use time selection)' also found a button on a toolbar with me. I find it very easy to select a time-region and click 'bounce' to only bounce that region instead of the whole track. Makes it easy for testing small parts, add enough room for reverb-tails in bounces, and prevent Reaper doesn't automatically add a little bit of length after the bounces .
My last tip for now, is for people who Bounce a lot during mixing or find they need to. Bouncing means you create a new track with the rendered audio, and the old one is muted. Default, this means that the plugins are NOT running on the old muted track, which is what you want. But if you load your project, all the Nebula instances on the bounced track still are loaded (and it can take a while). Well, you can select plugins in the track-FX window and instead of making them 'bypass' (untick the checkmark, or press ctrl+b) you can take the whole plugin offline (Ctrl-alt-b). That means the plugin is really unloaded from memory, and also is not loaded again when you load the project. But if you ever wanted to know or tweak it, you can bring it back online again by pressing ctrl-alt-b again. This way I don't have to wait and load Nebula instance which I'm not going to use (since tracks are bounced already), but I do have the settings still included in the project if I ever wanted to change something or look what I've used.