JohnMur

It seems that you would like the option of adding electronic sounds to your own USB recordings. In this case a DAW (Digital Audio Workstation) is the best approach IMO.

Although Audacity is free and a great music editing tool, for multitracking it isn't convenient and doesn't offer software instrument (i.e. synths, orchestral etc.)

1) Although you need to invest some time in learning the principles of DAWs like Ableton, once you understand one, you can then apply this principle to others like Logic, Pro Tools etc. in the future.
2) Although you may only use a small percentage of the functionality offered by a DAW, it is always there waiting in the background, waiting to be explored. Once you're production skills increase, or your artistic ideas become more complex, you'll appreciate these options.

Are you on PC or MAC? Personally I use Ableton but started out years ago to make music with MAGIX. It is a solid entry level DAW with an active community. That being said, there are an abundance of tutorials online and in youtube for Ableton...

JennyOndioline

This question is actually super relevant because if you're on a mac there's a good chance you have GarageBand built onto your HDD. It's not very powerful but it's a decent beginner's tool.

Otherwise I'm going to jump on the Ableton train. You can learn the basics of it in an afternoon. It looks more intimidating than it is, and unlike other DAWs, the more you master it, the more there is to discover. Before you know it, you'll be learning how to use even more powerful software.

Also, Ableton has a ton of extremely simple built-in tutorials. I'd recommend those over any youtube video if you're just starting out.