How to hear what you're recording?

Hello,
When I import some tape-recorded sound files (from a cassette-recorder plugged on the mic entry line) on my MacBook Pro, I can't hear the sounds at the same time. How can I do that?
I import some birdsongs in a sonogram software (Syrinx, Wildspectra), and I would like to hear the songs at the same time as the sonograms are created. Even Garageband doesn't allow me to hear the sounds while they're recorded.

Thanks
Sam

You need to turn on monitoring on the tracks. In the bottom of the right hand panel, you can turn it off, on, or input monitoring. Either on or input is fine

Thanks for your answer, it works for Garageband. Strangely, I have to keep Garageband open if I want to hear the input channel in the sound analysis softwares (Syrinx and Raven). It's a bit weird and strange, but it works.

I currently use Audacity to record using my Line In on my MacBook. As with most recording software (including Garage Band as mentioned below), monitoring needs to be turned on within the software's preferences.

The default Input needs to be changed in the Mac's Preferences to Line In as well. When sound is being sent to the Line In, you should see the Input Level changing in the Sound Preferences on the Mac.

So, what if you don't have Audacity or Garage Band open and you still want to monitor what you are sending into the Mac? Well, you can download a product called LineIn by Rogue Amoeba which will allow you to do the same. The only problem with the program is that you have to have it open to monitor just as you would with Audacity or Garage Band.

Now here's my problem I have with the Mac and I cannot solve for the life of me.....
I have a turntable hooked up to a mixer. The main output on the mixer goes to a receiver which has speaker wire heading out to my first set of monitors. These are not filtered through my MacBook at all. A second output from the mixer runs into the Line In on my MacBook. When I play a record on the turntable and try and monitor on both my first set of monitors and my computer speakers, the latency of the sound that runs through the MacBook makes it impossible to listen to properly. There is about an 1/8-1/16th second delay in the sound coming out of the computer speakers.

How do I get rid of this latency? Do I need to switch back to my PC which did this same thing without the delay?