Open a new project in Logic Express 9 by selecting "New" from the "File" menu. At the prompt, select "Software Instrument" as the track type. A new track and its associated channel strip will appear.
Open the channel strip's input menu by clicking the blank grey button beneath "I/O." A menu of available software instruments will appear. Select "EXS24 (sampler)" and "Mono" from the sub-menu. The "Stereo" and other options can also be used, but are not necessary because you will be working with a single, unmixed sound. The EXS24 interface will appear.
Open the EXS24's instrument menu and select "Factory." In the sub-menus that follow, select "03 Drums & Percussion," "02 Electronic Drumkits" and "Roland TR-808 Kit." The Roland TR-808's kick drum sound is traditionally used in creating bass drops because it is held, or "sustained," much longer than most kick drum samples. The EXS24 sampler uses the original TR-808 samples rather than synthesizing them itself, lending further authenticity.
Close the EXS24 interface. The TR-808 kick drum sound you will need is triggered by pressing the B0 key on your MIDI keyboard or Logic Express 9's on-screen piano keyboard. "Middle C" is located at C4, so the B0 key is three octaves plus one key to the left of "middle C."
Record-enable the track in Logic's Arrange area by clicking the track header; press "R" to begin recording. Record a single instance of the TR-808 kick sample and hold the note until the sample has played all the way through. Press the space bar to stop recording. A new MIDI region will appear on the track.
Right-click the MIDI region and select "Bounce In Place" from the menu. A pop-up menu will appear. Leave the default options as they are and click "OK." This will convert, or "bounce," the MIDI region you just created into an audio file on a new track.
Right-click the audio region you have just created and select "Strip Silence." In the pop-up menu, set the "Threshold" parameter to 1.0 and the "Pre Attack-Time" to 0.0040. Click "OK." All unnecessary silence you may have recorded with the original EXS24 MIDI sample will be removed.
Select the "Flex Tool" in Logic's Arrange area and click on the audio region. In the pop-up menu that appears, set the "Flex Mode" to "Polyphonic" and click "OK." Using the flex tool cursor, grab the upper right-hand end of the region and drag to the right. This will extend, or "flex," the region to your desired length.
Select the "Fade Tool." Click and drag from the beginning of the region to just past its right-hand end and release the mouse button. This will create an adjustable fade curve across the region. Right-click within the fade curve and select "Slow Down" from the menu. This converts the fade curve into a frequency curve, making it possible to slow down, or deepen, the sound while maintaining its length and integrity within the mix.
Click and hold the cursor over the frequency curve. By moving your mouse back and forth to manipulate the shape of the curve, you can now adjust the speed at which the sound deepens, or "drops." Experiment with different lengths and frequency curves to find the exact sound you want. A true bass drop needs to drop to about 20 to 30 Hz to achieve the full effect. Save the project so you can return to it to adjust your bass drop as necessary.