Ableton Live ships with two instrument plug-ins: Simpler and Impulse. This month we'll take a tour of the Impulse drum machine, discover how to create patterns to sequence it, and then look at some ways of increasing its powers using alternative routings and Rack combinations.
If you click on the Live Devices icon in Live's Browser, you will find the Impulse drum machine inside the Instruments folder. As with the other instruments, you can either drag the main Impulse folder icon to a MIDI track to create a blank Impulse, or open the folder and choose a preset with pre-loaded samples. The Impulse presets are divided into two folders (Acoustic and Electronic), both of which contain a mixture of raw Impulse patches and Group patches (Racks) that combine Impulse with additional effects.
To get started we'll load up the electronic preset called 'Studio Kleine'. As normal, either switch the MIDI track to the 'In' monitor mode or record-enable the track, and you will be able to play Impulse. You can trigger the samples with the mouse, the keyboard, or a MIDI device. To trigger with the mouse, move the cursor over any of the square sample slots and click the Play symbol that appears. This isn't very practical, as it's too easy to accidentally click the mute or solo buttons, so it's much better to use the computer keyboard. The middle row of keys (A-K) is mapped to Impulse's sample slots, and this is a very effective way of playing Impulse, especially if you are out and about with a laptop that has no MIDI gear attached. However, to be able to play with different velocities, you need a MIDI keyboard or trigger pad. Somewhat unconventionally, Impulse is mapped to the C3-C4 keys on the white keys only. Later on we'll look at how to change this key-mapping.
Once you're up and playing, you can record MIDI Clips in the track in the standard way, using either the computer keyboard or MIDI triggers. However, we're going to look at how to create drum patterns by drawing into a grid. First, double-click in an empty slot in the MIDI track containing the Impulse. This will create a new, empty one-bar Clip. Display the Clip in the Clip View area and reorganise the window so you get a decent area to work with. You can make the Clip View area larger, and also resize the note and velocity sections. Next, click in the Length field and change it to two bars so that you have a longer loop. Because Live recognises that there's an Impulse on the track, the edit area doesn't contain the usual MIDI note (piano roll) display. Instead there are just eight lanes, labelled with the sample names loaded into Impulse. Before entering any notes, go to the Options menu and check that 'Snap to Grid' and 'Fixed Grid' are both enabled. Then right-click on the edit area and choose which grid resolution you want to work with. This will be displayed at the bottom-right of the edit area. You're now ready to start creating a pattern. Enter Draw Mode by clicking the pencil icon in the main tool/transport bar, and click anywhere in the grid. Red blocks appear where you click, representing notes, and if you click on any block again (see top screen opposite) it will be deleted. Play the Clip and you can work on your pattern as you listen to the loop. You can audition any sample by switching on the blue headphone icon above the Browser and clicking in the box to the right of each sample's name.
If you switch off Draw Mode, the cursor returns to being a standard arrow and takes on different functions. Clicking on a note now selects it, and you can pick notes up and move them around. Double-clicking a note deletes it, while double-clicking an empty square in the grid creates a note there. When the cursor is near the edge of a note, it turns into a trimmer, allowing you to make notes shorter or longer. Note that each sample in Impulse can be set to either Trigger or Gate mode. In Trigger mode, a sample is only played for the duration of the MIDI note, so is affected by trimming. In Gate mode the sample is played in full no matter how short the MIDI note.
Velocity is edited by clicking the head of the 'stalk' underneath a note in the velocity graph and moving it up or down. Often it is unclear which stalk belongs to which note because two or more notes are at exactly the same time. Hovering the mouse cursor over a stalk head highlights the note it belongs to in blue. If both notes are the same velocity, select the note you want to adjust first, and its velocity stalk will be selected when you click on it. Draw Mode can be used to quickly add velocity variations across a whole pattern. If you click and draw an imaginary wavy line across the velocity graph in Draw Mode, all the velocities will snap to this curve. However, you wouldn't normally want to do this for all the different samples at once. If you want to, say, adjust all the closed hi-hats, you need to select them all first. The shortcut for this is to click in the audition box for that sample. Now if you hold down Shift when you draw into the velocity graph, only the selected notes will be affected. As you can see in the screen above, the relative velocities of the notes are indicated by how boldly they are coloured.
Let's turn our attention to Impulse itself. Impulse is quite a simple drum machine, offering eight channels, each of which can only play back a single sample (there's no velocity switching). However, nearly all the parameters can be set differently for each channel (sample), so you can create a large number of different-sounding kits from just a few basic samples. Only the three knobs on the right of the Impulse panel are global (Volume, Time, and Transpose). Every channel has the parameters you might expect: Sample Start, Volume, Pan and Decay. Each sample also has its own multi-mode filter, and a Saturator with drive control. Things get more interesting with the Transpose and Stretch controls. Both of these can be controlled by velocity for some really cool effects. In fact, four separate parameters on each channel can be velocity controlled, and the Transpose, Pan and Filter Frequency parameters can be given between zero and 100 percent randomness. This brings a lot of variation and movement into a drum patch and gives Impulse its own character. All the channels have the same set of parameters except for channel eight, which has an extra button called Link. This turns on what would usually be called an 'exclusive group' mode with channel seven, allowing you (typically) to set open and closed hi-hats to cancel each other.
A sample can be added to a slot in Impulse by dragging the sample from the browser or from the desktop. This replaces the sample that was in the slot, but keeps the parameters the same. You can also take advantage of Live 6's new 'Hot Swap' functionality to step through different sounds while a pattern is running. To do this, first hover the mouse over a sample slot in Impulse and click the Hot Swap icon that appears. The icon turns orange, as shown in the screen below. You can now find a folder in the Browser and select a sample. Pressing Return puts the selected sample into the slot. Use the mouse or cursor keys to select other samples and hit Return (or double-click) to load them.
Let's look at a couple of tricks that can extend the power and flexibility of Impulse. Firstly, you will have noticed that Impluse has no onboard effects beyond the Saturator. You can, of course, drop effects into the MIDI track after the instrument to process its mixed output, and this is what many of the preset Racks do. But what about individual channels? Impulse is cleverly integrated into the Live mixer so that you can route individual channels to different tracks. In the screen above, the kick drum and snare drum channels have been routed to two separate audio tracks. This is set up in the tracks themselves, by choosing the Impulse track as the input source and the specific sample as the input channel. The selected sample is then routed to this track and is automatically excluded from the mixed output of Impulse. Different audio effects can then be placed on the individual tracks. Monitoring of the signals is achieved by putting the track into 'In' monitor mode. You can also use this method to record all the individual drum parts as audio Clips.
The final trick is to create drum patches with more than eight sounds, with the samples spread across more MIDI keys than Impulse's fixed default of C3-C4. The extra channels are gained by layering more than one instance of Impulse in a Rack. We'll use two Impulse presets to make things easier: the 'Studio Kleine' preset, which has good basic drum sounds, and the 'Artefact Delerium' preset, which consists mostly of effects. 'Studio Kleine' is already running in a track from the previous examples, so the first thing we need to do is change the MIDI key mapping, or both Impulses will be layered on top of each other in the C3-C4 range. The simplest way to achieve this is to use the Pitch MIDI effect, which simply transposes any incoming MIDI notes by a set number of semitones. Choose Live Devices in the Browser, and open the MIDI Effects folder. Open the Pitch folder, and drag the preset '+24' into the MIDI track, where it will appear to the left of Impulse. Any MIDI notes coming into Impulse (both from your MIDI keyboard and from MIDI Clips) are now shifted up two octaves, and the drum machine will now respond to the more standard C1-C2 notes.
Now, select both the Pitch and Impulse devices, and choose Edit / Group. The two devices will be placed into a Rack. Click the Chains icon (three horizontal lines) in the Rack header to view the Chains List. Chain one is your Pitch/Impulse combination, so rename it appropriately. Next, open up the Impulse preset list in the Browser and drag it into the Chain List. Both Impulses are now part of the same Rack device (as in the screen below) and can be played from different octaves of the keyboard. You may want to use another Pitch device to remap the keys the 'Artefact' patch responds to. However, be careful not to overlap the instruments — unless you want to, of course!
If you're feeling extra adventurous, you might consider using the Scale MIDI plug-in to map the samples to exactly the keys you want, including the black keys. The bottom screen shows a Scale setup that maps an Impulse to the first eight keys from C1. The Transpose parameter does the same thing as the Pitch effect, namely shifts everything by two octaves, while the matrix remaps keys within the octave. The 'X' axis of the grid represents the 12 MIDI keys in the octave. The 'Y' axis represents which MIDI note each key is transposed to. For example, in the second column from the left (representing the black note C#) the orange marker has been placed in the third row (representing MIDI note D). Thus a C# MIDI event going through the Scale devices emerges as a D. The result is that the Impulse sample previously played from D is now played from C#.