In Pro Tools LE the actual audio file which you record does not get rendered by a RTAS or AU Plugin until you mix down or bounce. This allows you to change the sound after. For example: IKMultimedia's Amplitube plugin for guitar will make your guitar sound as if it were recorded through an amplifier, remove the plugin and you're left with an untreated version of the guitar track.

To apply a plugin to your trumpet you need to 'plug' it into the channel (track) you recorded it to. Open the Mix window (assuming your trumpet is on Audio (track)1) and at the top of the channel strip are five insert points. Use the mouse to open the top insert point and a menu of plugins should drop down. Choose the plugin you want by simply clicking on it and presto it opens. Change parameters on the plug if you wish.

You can insert a plugin before you've recorded the track thus monitoring the processed sound or you can if you wish plug it in after you've recorded. PT LE allows for 5 plugs per track.

You can also highlight the audio sample you want to effect and apply an Audio Suite plug-in. This creates a new soundbite, but the original is still in you bin on the right side.

The third option is to send it out to a bus and insert the plug-in on the bus return. This is nice if you have multiple sounds to which you want to apply the same effect. You can then bounce the original track(s) and sub mix, opening up some more tracks; i.e, you have laid down six trumpet parts. Assign them all to bus send 1&2. Put your effect on the return bus 1&2, and assign the output of ALL of the trumpet tracks and the Bus return 1&2 to bus 15&16. Select a stereo track and make the input bus 15&16. Once you are happy with your levels record the results. Voila! you have freed up four tracks!