1) Select File>New, and choose 44,100 Hz, 16-bit, mono to create a new window for your sound.
2) Select Tools>Synthesis>Simple to open the Simple Synthesis dialog box.
3) Set the amplitude parameter to 0 dB.
4) Set the Waveform Shape parameter to Sine.
5) Set the Length to 0.100 seconds.
6) Set the Frequency to 50 Hz.
7) Click OK.
Hit the space bar on your computer keyboard to play the sound. Cool, isn't it? It's also very quick in duration, but that's what you need because you'll be using it in conjunction with your bass sound.
Now if you'd like to use the sound in your sampling hardware or software, just save it as a WAV file. Then import the WAV file as a new sample (this procedure varies depending on your sampling hardware or software) and you're ready to start triggering your new sound via MIDI.
If you don't have sampling hardware or software, you can also import the WAV file into your digital audio sequencing software. Let's use Cakewalk for this example...
1) Select the Track to which you want to import the WAV file.
2) Set the Now Time to the beginning of the project.
3) Select Insert>Wave File.
4) Choose the WAV file and click OK.
Now just use this Track to hold your new WAV sound sample, and simply copy and paste the sample into another Track so that it coincides with each note in your bass Track. Now whenever a bass note plays, it will get an extra boost from your boom sample. Just be careful not to play your music too loudly, because you're sure to get complaints from the neighbors!