I'm a complete beginner at Logic Pro X and ever since I've been trying to mix something there I get this question and haven't found any answers to this. Is there some way to change effects (or pan) within the track? I mean, I play one note and how can I change effects of this single note within a track without changing the effects on the entire track? And how do I pan i.e a single note of a software instrument?
If the software instrument doesn't support panning individual notes, you have to make another track and pan that.
Alternatively if you just want to pan different parts of the recording, then you can turn on automation (press a) and then on the track select pan, and then automate the parts of the track you want panned differently.
What you're describing sound like you are looking for the Automation feature. Automation is a functionality offered by pretty much any DAW (Digital Audio Workstation) that allows a user to change the parameters on a given track over the course of time. Depending on the DAW, you are able to automate anything from just Gain (usually thought of as volume by those less familiar with audio processing) to every specific aspect of the track, such as Gain, Panning, settings on a particular effect, etc. Fortunately for you, Logic has great functionality for automation.
I am still on Logic 9, so some of my direction for accessing the different aspects of the automation functionality may not be exactly how to access things in Logic 10.
There are two ways (that I am readily aware of) to access the Automation functionality in Logic. First, my preference, is to press the 'A' key, second is to click the 'Automation' icon in the header of the window. Once you toggle to the automation view, you should see the tracks all change a little, usually expanding vertically and showing a line across the length of each track. By default, each track's automation is showing Gain, so that is the easiest place to start. The line across the track represents the current level, so if you have several tracks that all have different levels set, you should be able to notice that the vertical placement of the line is different for each track. To start, this line appears somewhat grayed out, which indicates that there is currently no automation. Start by clicking on the line and you will see a Node placed, which looks like a little circle on the line, and the line will illuminate. Next, click elsewhere on the line to create a second node, then click and drag the node up or down. You will see that the horizontal line will come in flat from the left, then a diagonal line between the two nodes, then continue to the right flat again. For example, if you set your first node at 0 Gain and your second a -15, then everything preceding the first node will output based on a 0 gain setting, then decrease in gain over time between the two nodes, then proceed at -15; this will ultimately cause your actual volume output from your speakers to decrease as it follows the line through time.
From here, you are able to access the additional settings to automate by choosing them. Again, this is Logic 9 directions, so I hope they are relevant in Logic 10. In the left side of the Arrange window, each track is displayed, along with its name and a logo. When you have the automation view toggled on, you should also see a dropdown menu. Since the default is Gain, you should see Gain or Volume as the selection in the dropdown menu to start. Click on this and below you will see the different parameters for the track. Panning will be one of the options you see but may be in a sub-menu of the dropdown. You should also see each of the plugins that you have on your track and that they each have a sub-menu as well, within which you should find each of the different parameters for that plugin. For example, a compressor will have the options of Threshold, Ratio, Makeup Gain, etc.
If you want to utilize automation of more than one parameter for a given track, you will need to expand the automation window for that given track. In Logic 9, this consists of clicking the little arrow in the bottom left of the track. This will open an additional automation field, which can be assigned to any of the parameters of the track and will allow you to have more than one thing automated. You will typically find that different parameters will have a different color associated with them. If you toggle the automation view off and back on again, the multiple parameters being automated will collapse, only showing one, but you should see the different lines that represent the automation overlayed. To access the additional parameters, you just need to click the arrow again. If you have more than two, you will need to click the arrow a couple times to access all of the parameters.
There are some great automation tools and shortcuts that you can use to have smoother and/or more efficient functionality. I won't go into many but one example that is very useful is the automation curve tool. In the upper right of the screen (again, Logic9) you can assign the mouse functions for primary and secondary mouse clicks, one of the options being the curve tool. This allows you to have a smooth curve in your automation without having to create a lot of nodes. There are several curve options, which are a little weird to get used to but you can just click the area that you would like to curve and drag it up/down/left/right and you should see the different options visually. If you would like to see some more of the automation functions, you can open the keyboard shortcuts menu and type 'automation' into the search field, which will pull up all of the functions, one example is a function that will create automation nodes at the borders of a selected region.
One thing to keep in mind is that creating automation for a given parameter will mean that you have to make all of your changes to that parameter using automation. You will find that you are still able to make the change elsewhere but it will ultimately revert to the automation. For example, if you set up automation for the gain on a track, you will still be able to move the slider up and down to change the gain setting but as soon as it reaches one of the nodes in the automation, it will snap to that and continue following the automation. Because of this, I typically try to set everything up at the most common settings, then begin automation. This makes mixing a little easier for me. You can also toggle the automation off for a given track by setting it to off and back on again by setting it to Read. Once you start automating a track, you should see a few spots (in the track itself and in the mixer view) where it says Read and you can use the dropdown menu to explore the options, including one to write, which can be used to either draw in your desired automation, or you can use a midi controller while the track is playing to write in your automation.
The other option I could offer to accomplish your goal, would be to create a duplicate track (cmd+d) and create a region containing the notes you want the different effects for on the duplicated track, then make the changes to your plugins/panning. This is a little easier in one regard but if you have more than one change you would like to accomplish throughout the course of the song, you will end up needing to have multiple duplicates, which is less efficient and uses more processing power.
Given the fact that I don't have Logic 10, I hope this is all relevant for you!