So I’m making a really simple song mashup as a joke (and practice, because I’m really, really new). However, the problem is that one song has a really high pitch, and one song has a really low one. Is there a tool to even it out a bit, or a way for me to do it manually? Thanks.
(I use win7)
You probably don’t. The movie people do a video bumper to get between them and the club DJs do a clip segue, where they stop one song dead and then start the new one. Not all songs lend themselves to graceful cross fading.
Koz
A “tape-stop” or “turntable-warp” effect could be used to gradually [glissando] drop the pitch [and tempo] of the high track. It will sound comic though : as if power had been cut to a record-turntable or tape-player causing them to slow to a halt in [say] half a second. A turntable-warp plug-in for audacity is here … Missing features - Audacity Support
Audacity’s built-in effect “Sliding-time-scale/pitch-shift” is another method , which has the option of keeping the tempo constant whilst gradually lowering the pitch.
Done 
https://drive.google.com/file/d/0By1nks3O7GFZN1dNbmRGczFyVmc/view?usp=sharing
I fixed it by just increasing the decibels of the other song.
Which song?
The second song is badly distorted because it is too loud.
Audacity may not show you overload and distortion until you export a sound file. If you didn’t listen to it after the export, you may not know it doesn’t sound very good.
Koz
I did listen to it after export. It sounded perfectly fine to me 
Could it be the speakers?
The second part needs to a tad unpleasant though. It’s a prank, after all.
Not my speakers 
The second part is very badly distorted - ok if that’s wjat you wany 