I am working on restoring some music from my band in the 70s. It's a combination of tape and LPs. What is a good plug in to reduce tape hiss and LP crackle?

https://www.izotope.com/en/products/master-and-deliver/ozone/ozone-elements.html
 
They also make other versions and the price goes up, I think you can demo for free but this is the go to of most people who do transfers. 
Sonys Sound Forge also is worth checking out, I have the free version came with my Sony USB turntable and it does an amazing job on old LP's. 

Not sure if that's accidentally the wrong link, but Ozone Elements is not the right product for this task. Certainly won't do anything for hiss and crackle. Izotope RX is the product you need for this. Again, comes in a range of prices and versions.
 
https://www.izotope.com/en/products/repair-and-edit/rx/rx-advanced.html
 
The noise reduction and decrackle tools in RX are absolutely as good as it gets.
 
 

similar thread http://forum.cakewalk.com/FindPost/3245843

I personally use Ozone RX myself and it is well worth the price.
However if your just doing some home studio stuff trying to find a medium grade noise gate,
this one does the job and is free: http://www.vst4free.com/free_vst.php?id=853
 
I've used it to gate drums. Its not deep in features but it does the job.

Hi. I bought the RX Elements, and the Standalone version of that is actually quite good (espesially for the 29$ price I got it for).
I think it is available as a demo.
The bigger brother is certainly a better choice if funds permit.
If not, the Elements version would be my budget tip.
All the best.

If you just have an expander you can remove lots of noise.

I would probably send to 5 aux tracks. Include a Sonitus Multiband and solo a different band on each of the five. Then your expander of choice.

If you want to mix in the original, use a sixth aux track.

Don't forget, to have proper signal for setting the expander you might want to raise gain prior to the expander then restore it after. FX chains are perfect for this.

https://youtu.be/sctKIMAunhk

I could have sworn this thread said "Noise gate".
sorry, disregard my first comment.

I use the ReaFIR plugin that is part of the free ReaPlugs.  I got it a few years ago from the Reaper site here: https://www.reaper.fm/reaplugs/
 
You use the plug to sample a segment with just the noise you want to remove to create a noise profile, then use the plug to apply noise reduction using the noise profile to the segments that you want to remove noise.  It works pretty well.
 
Hope this helps,
Paul

Izotope RX.