Tuning the drum samples in your song is an important but often overlooked technique in electronic music production. Like any musical instrument, a drum plays at a certain frequency, or pitch. Every frequency corresponds to a certain note on the musical scale.
If the drum samples in your track are pitched to notes that are out-of-key with the rest of the song, they can sound slightly but frustratingly "wrong." Use Ableton's built-in Spectrum frequency analyzer plug-in to determine the pitch of a drum sample, then use the Drum Rack's Transpose function to move the sample's pitch into the same key as the rest of the track.
Load up a Drum Rack in Ableton, then add a synthesizer plug-in to a second MIDI track. Select one of the synthesizer's pad presets. Drop a snare drum sample into a slot on the Drum Rack, then open the piano roll editor and put a snare on every other quarter note. Program a chord into the synthesizer's piano roll. Here, I'm playing a G major chord -- G, B, and D -- but you can use any chord you like.
Drop Ableton's Spectrum plug-in onto the Drum Rack. Play the drum track, then look for the highest peak on the Spectrum display. Move the mouse cursor over the peak to see its frequency and the corresponding note. Here, we can see that the snare drum's dominant pitch corresponds to the note F#, which isn't a component of the G major chord. We'll need to change the drum's pitch so that it matches one of the notes in the chord. Because we want to change the sample's character as little as possible, we'll move it to G -- the closest note to F# in the chord.
Set the snare drum's Transpose control in the Drum Rack to "1." This brings the snare drum's pitch one step upward to G -- the root note of the G major chord. Because we're only moving the pitch by one step, the sonic character of the drum sample doesn't change drastically, but it fits much better with the synth. Listen closely to the audio sample to hear the subtle but noticeable effects of tuning a drum sample. In the first and third bars of the loop, the snare drum is at its original pitch of F#; in the second and fourth bars, it's transposed up to G.
When you add other drum samples to the drum rack, tune them to the same key. The drums don't all need to be at the same note, as long as their notes are all part of the relevant chord. For example, in this situation, the kick drum could be transposed to B, the snare to G and the hi-hat to D. If you find that you need to transpose a drum sample's pitch by more than a few steps, consider using a different sample, as large changes in pitch can make the drum sound very different.