Every track you add to your recording, and every plug-in you use, consumes a little more of your computer's processing power. Unless you are a really light user with low ambitions for your project, you will often find that you are running up against the limit of what your computer can do. It just can't calculate fast enough.
Some plug-ins are relatively 'cheap' to run, in the sense that they don't consume much processing power.
Other plug-ins are 'expensive', either because they work very hard or because they have been poorly designed in that respect.
It's difficult to make a mix using nothing but cheap plug-ins though, particularly if you want great reverb.
So what can you do?
Well, you could buy a faster computer. A faster computer is always a better computer, although clearly this is going to be a costly option.
You could increase the buffer size. That's a piece of memory that is held in reserve for the computer to do its calculations. But you might still be recording new tracks, and increasing the buffer size increases the latency, or delay, between input and output. Or you might have increased the buffer size all the way already.
There is one solution however that costs nothing and is almost limitless in scope, and that is to 'freeze' tracks that have plug-ins inserted.
This means that the track is re-recorded, or bounced, back to disk, with all its plug-in effects applied. So the result is a track that sounds like you want to hear it, but it doesn't need plug-ins because the effects have been embedded into the audio.
One drawback of this is that once you have frozen a track, you can't make any adjustments to the plug-ins other than by going back and unfreezing it. Even so, this is a price worth paying to get the degree of flexibility you need.
Some DAW softwares make freezing and unfreezing very easy. This is to be commended; all DAWs should be this way.
However some DAW softwares are surprisingly lacking a freeze feature. All is not lost however as you can do it another way…
1. Route the output of the track to be frozen to an unused bus.
2. Make a new track and set its input to the same bus. Set it to record-ready.
3. Hit record and play the track through.
Simple! You now have your frozen track. You can deactivate the first track, but it can remain in the session if you need to go back to it.
In summary, when computers are ten times more powerful than they are now, freezing won't be necessary and we will be glad of that, Until then however, freezing is an important technique for unleashing virtually all the power you can handle.