loads of tracks slow performance

I have at the moment got 67 midi tracks (not even got any drums or percussion yet) but at certain points in the track my CPU jumps up and I am unable to do any type of mixing as I cannot hear the track. If I turn off the playback it runs fine but is a bit pointless as I cannot hear it to see what needs to be changed.

As a temporary measure, while you work on upgrading your Mac and/or what else you might need to do.......

Freezing some tracks would probably help a great deal....

https://documentation.apple.com/en/logicpro/usermanual/#chapter=9%26section=16%2 6hash=apple_ref:doc:uid:TempBookID-Repla…

What you do is mix in sections.... and then freeze/unfreeze those sections....

So, for example, mix your drum parts and then when you have that section mixed, freeze those parts and move onto the next section and so on...

Freezing, frees up your CPU for other tasks.. so you have to plan ahead a bit... to get the most of it... and yes, there will be some limitations as you have mentioned but again, with some preplanning, you can make it work.

Note: Even on the latest Macs running the latest OS X / Logic pro X combos.. for larger projects, Freezing is still an essential part of optimizing performance in a lot of cases.

Also, if you are using multiple FX plugins..... with the same or similar settings on multiple tracks.. Start using Buses/Auxes to reduce the number of different FX plugins...

As for your actual issue..

Your Mac is simply not powerful enough to handle the projects you are creating...

But, unless you are willing to buy a new Mac.....

Things you should look at upgrading would be;

RAM (making sure you run Logic Pro 9 in 64bit mode to take advantage of that extra RAM) will help to some degree depending on what your projects contain. Example: The more samples you are using then more RAM will help...

Rolling back to Snow Leopard rather than using Lion... as SL + LP9 is still the optimal combination of OS X and Logic at this time... (Better than any OS X and Logic Pro X combo I might add..) Note; Modern Macs cannot run Snow Leopard.... as SL doesn't have the support for the latest hardware in modern Macs..

However.. given the age of your iMac and it's specs.. and the size of projects you are trying to create.. I think your best bet is going to be.. buying a faster, more capable Mac... One that has an i7 Quad Core and is upgradable to at least 16 GB RAM... The 2011 iMacs work very well in regards to this.. I have two 3.4Ghz i7 16 / 32GB Ram 2GB VRAM 27" 2011 iMacs... running SL and LP9 and frankly they outperform the more modern iMacs running Yosemite and LPX by some degree.

You can still find these 2011 iMacs if you search carefully.... They even still appear on the Mac Refurb store from time to time.. at a great price and with the full normal Apple Warranty...

Besides that model, if you are going to buy any new Mac, the Apple refurb store is one to check first.... for good pricing..

This third party website is great for finding out what is, and tracking the prices of stock in, the refurb store..

https://www.refurb.me/us/

I was using Absynth which is not 64bit,

There is a newer version which is 64bit AU... but that might require a paid upgrade depending in which version of Absynth you have...

Bear in mind too, that when you run LP9 in 64bit mode.. a built in 32bit to 64bit bridge will allow your older 32bit only AU plugins to run in 64bit Logic Pro 9.

Logic Pro and MainStage 64-bit mode FAQ - Apple Support

ada mann wrote:

Hi

I am running Logic Pro 9 on a iMac 21" (2.4ghz C2D, 4gb Ram OSX 10.7)

I am trying to make some scores for games, films etc using a simple midi keyboard and using the built in sounds and samples from logic but will want to change these later when I can get some amazing and realistically sounding samples

I have at the moment got 67 midi tracks (not even got any drums or percussion yet) but at certain points in the track my CPU jumps up and I am unable to do any type of mixing as I cannot hear the track. If I turn off the playback it runs fine but is a bit pointless as I cannot hear it to see what needs to be changed.

They're not "just" MIDI tracks, if you're using virtual instruments a complete synthesizer is built in RAM and uses the computer's CPU to do all the calculation necessary to produce sound. What you've described seems pretty normal to me. If you're thinking about using "amazing and realistically sounding samples" you will need a lot more machine, both memory, and especially CPU speed, also more processing cores.