Manuel de Hydrogen

From the "Audio System" tab (Figure 1.1) it is possible to modify the audio driver being used (OSS, Jack, ALSA, PortAudio) with its buffer and sampling rate (unless using JACK, in this case the audio driver configuration should happen before starting the JACK server).

We can set some features of Hydrogen like "Enable track outputs" useful if you want to add effects to a single instrument with jack-rack. "Connect to Default Output Pair" connects the output to the default ports: uncheck this if you want to connect JACK output to other ports without disconnecting them first

Keep also an eye on the value of "Polyphony": depending on your CPU you may want to change the max simultaneous notes in order to prevent hydrogen from overunning the audio driver.

Figure 1.1. The Audio System Tab

The following drivers are available:

The "Midi System" tab (Figure 1.2) concerns the MIDI input. You can choose the MIDI driver and input, setup channels, binding actions to MIDI events.

Figure 1.2. The MIDI System Tab

The "Appearance" tab (Figure 1.3) let's you to modify Hydrogen and QT graphical properties.

Figure 1.3. The Appearance Tab

The audio engine info is a window with various stats about Hydrogen and the audio driver. In case JACK is used, buffer and sampling rate should be set before starting Hydrogen (JACK automatically starts when an application tries to connect).

Figure 1.4. The Audio Engine Info Window

It is possible to change tempo at any time using the tap-tempo and BeatCounter features of Hydrogen. You can change these while playing or while the song is stopped. To change the tempo, hit the , (comma) key in tempo for the number of beats in the measure. After the correct number of beats are met, the tempo will change to the average tempo that you tapped in. If you continue to tap, these new taps will become a part of a rolling average. If you tap accidentally, or if you wait too long between taps, the tap tempo counter will start over.

The Tap Tempo is a part of the BeatCounter, which is essentially a Tap Tempo on steroids. By default the BeatCounter display is not visible. To see the BeatCounter widget click the upright button (BC) between Song/Pattern mode selector and the BPM-widget. Or, it can be shown by pressing the comma key (,).

The tempo that you tap will be considered even beats of the beat type. The beat type can be set to 1/8 (for eight-note beats), 1/4 (for quarter-note beats), 1/2 (for half-note beats), and 1/1 (for whole-note beats). To change the beat type use the left arrow buttons. To change the number of beats that are counted, use the right arrow button. You can set from 2 to 16 beats. (I.e. if you set the beat to 6, you will have to tap 6 times before the new tempo is computed and set.) When the display shows an R, it means that the BeatCounter is ready to start from 0. Every time you tap with the comma key, it will show the number of taps that you have entered (1, 2, 3...).

The button in the bottom right-hand controls the auto-start feature, and it toggles between S and P. When it shows P for (Play), the song will set the new tempo and automatically start to play after you tap the right number of beats (if it's not already playing, of course). This way, if you have the BeatCounter set up for 4/4, you can tap 1-2-3-4, and start playing on the next beat. When it shows S (for Set BPM), the auto-start is disabled.

For example: Suppose you have a live band, Hydrogen, and a softsynth that is controlled by Seq24)... and you want them all to start at the same time. Set the beat type to 1/4 and the number of beats to 4. Enable auto-start (button shows P). Count off the band 1-2-3-4 (while tapping the comma key) — and everyone starts on 1.

Another example: Same situation, but the song doesn't require Hydrogen or synths until some point later. During that time, a human (e.g. guitar player) will be setting the tempo. On the measure before Hydrogen is supposed to play, tap the comma key 1-2-3-4 with the beat... and you're in on the next beat (at the right tempo).

If you are using the JACK Transport, the BeatCounter continues to work. If another program is the JACK Transport Master, Hydrogen will respond to tempo change events from that application. Note that in this situation, Hydrogen is supposed to be a slave, so some of the BeatCounter features will be disabled or will not work properly. If Hydrogen is the JACK Transport Master, tempo changes from Hydrogen will be reflected in those programs (if they support it).

Some of the settings to adjust the BeatCounter's latency compensation, and they are located on the General tab of the Preferences Dialog ( Tools → Preferences ). Here there are two spinboxes:

Note that these can be set to positive (+) or negative (-) values. In order to find useful values for these, you will need to take some time to play with it. Also, you may want different values depending on the speed of your hardware, audio devices, drivers, etc. Using the BeatCounter effectively requires practice.

This lists the drumkits that were installed by your system administrator. It was determined by the compile-time prefix. On Unix-like operating systems, this is usually /usr/share/hydrogen/data/drumkits, or possibly /usr/local/share/hydrogen/data/drumkits. These kits are available to all users on the system, and users are usually not able to add to them.

To load a drumkit from here, right-click the drumkit and select Load. This will replace your current drumkit with the one that you selected. To load a single instrument from that kit, left-click the plus to the left of the drumkit's name to show all the instruments. With your left mouse button, click and drag the instrument into your current kit. The instrument will be added to the drumkit that you currently have loaded.

These are your own drum kits that you can manage yourself. They are usually stored in $HOME/.hydrogen/data/drumkits. When you are creating a new drumkit, you can save it here by selecting Instruments → Save library.

Loading drumkits and instruments to use is the same as for the System Drumkits (see Section 7.1).

Before you save your favorite patterns to the sound library, be sure to edit it's properties by right-clicking and selecting Properties. There, you can give the pattern a title and a category. You can use one of the categories already provided, or create your own categories by simply typing in a category name. The category name is important, because the patterns will be filed by category in the Sound Library.

You can save your favorite patterns in the sound library by right clicking the title of the pattern in the song editor, and selecting Save Pattern. It will appear in the Sound Library underneath Patterns and the category that you assigned to the pattern.

To save songs in the Sound Library, put them in your data directory underneath the songs folder (usually $HOME/data/songs. To remove them, remove the file from that folder.

The synthesizer in Hydrogen is a sample-based synthesizer. A sample is a piece of pre-recorded audio (usually between .1 sec and 3 sec). To play a note, the sample is simply played back at the right time. There's a few concepts and terms that you should understand when you are putting together a drumkit. (See Glossary for more detailed explanations.)

Typical samples that are used in Hydrogen are: the sound of a single drum hit, the sound of a single cymbal hit, the sound of a single cowbell hit. Whenever you put a note in the pattern (or play a note using MIDI), Hydrogen will play whatever sound you have loaded. So, to put together a drum kit you need to gather short recordings of the bass drum, each tom, each cymbal, the high hat open, the high hat closed, the snare drum (snare on), the snare drum (snare off), rim shots, etc.

However, there are no rules about what a sample can be. It's not uncommon to use Hydrogen to trigger non-drum sounds like: audio clips of people talking, a clip from a song, sound effects, audio clips from movies, and famous people speaking. Be creative!

To start a brand new drum kit, select Instruments → Clear All. This will give you a bank of 32 blank instruments. To delete instruments, right-click on on each instrument and select Delete Instrument. To add more instruments, select Instruments → Add instrument.

Select an instrument to start editing it. This is done by left-clicking on the name of the instrument in the instrument list (at the left). You will notice that the name of the instrument in the Instrument Editor matches the one that you clicked.

After you have your drum kit working the way you want, select Instruments → Save library. It will ask you for the name of the kit to save. If you wish to overwrite an existing kit, you will need to type in the same name as the kit that you want to replace.

Drumkits are automatically stored in the data directory (i.e. $HOME/data/drumkits).

To export a drumkit (for sharing with others), it must first be loaded into your Sound Library. Then, select Instruments → Export library from the menu. Select the drum kit that you wish to export, and give it a file name to save it to.

For each instrument in a drum kit, you can load several samples and set different synthesizer parameters. This section will step you through how to create a new instrument and load the samples.

To begin creating an instrument, select Instruments → Add instrument. This will give you a blank instrument to start from.

Now, you need two samples. Any .WAV or .FLAC file will do. Hydrogen provides several in the data/drumkits directory.

In the instrument editor, click on Layers. You can layer several samples into the instrument. Which one is played depends on the velocity of the incoming note. Click Load Layer and point the Audio File Browser to your sample. Note that the Audio File Browser will allow you to preview the sample before you load it. It will also allow you to load more than one sample at a time. But for now, only load one.

After you load the sample, you'll see that there is now a 1 at the top, and the topmost rectangle has turned light blue. To load a second sample, click the slot just below it, and then click Load Layer to bring in another sample.

After bringing in both samples, you'll probably notice that only the first sample is being played whenever you trigger the instrument. This is because you need to set the velocity ranges for the layers. Move your mouse to the sides of the light blue rectangles and you see that you get a left-right drag cursor. Now drag the sample to the left or right (like a curtain). You will now see Layer 2 appear.

The velocity setting for the layer is 0-velocity on the left, and full velocity on the right. Set up Layer 1 to sound for soft notes, and Layer 2 to sound for hard notes. (I.e. Layer 1 on the left and Layer 2 on the right.)

Now, in the pattern area, set up a simple pattern that plays this instrument. Adjust the velocity settings on each note so that you can get the different samples to sound. Now set the pattern to loop and notice how your different samples are getting triggered. (To learn about editing a pattern, see Section 5)

For each layer, you can set the Gain and the Pitch. The pitch also has a Fine adjustment.

Use the Gain adjustment to control how loud the sample will play. This is necessary because it's extremely difficult to get a set of samples that all sound at about the same volume. By adjusting here, the samples that were recorded too quietly can be turned up to match your loud samples (that had to be turned down).

The pitch of the sample can be modified with the pitch controls. The Pitch knob adjust the pitch in musical half-steps. (So, -12 is down 1 octave). The pitch on the right adjusts the pitch ±50 cents. (One half-step is 100 cents.)

In the instrument editor, click on the General button. Here you can adjust several parameters that are for the whole instrument (not for each layer). The parameters that you can adjust are:

It's important that you understand Section 8.1 in order to continue on.

With all of the different parameters available to tweak, it can be difficult to set up something that sounds nice when you're done. Here's a few tips on setting up an instrument:

Turn down the gain. Every time you have a gain knob (i.e. an amplifier), this is called a gain stage. With every gain stage you have, it's easy to overdrive your signal — which means the signal gets distorted by clipping. In addition, if you have two samples that, by themselves, peg your meters — what do you think happens when you combine them? That's right, you overdrive the signal again.

If things sound bad and distorted, start by turning down the gain setting on the layer... especially if it's larger than 1.0. Then turn down the instrument gain. Then any gain on a LADSPA effect. Then the fader on the mixer. Then the master output fader.

Test samples at full velocity. Your sample will be played louder if the velocity is higher. So, if you set everything to sound nice and full with velocity at 0.7, what will happen when you get a full velocity of 1.0? (Hint: clipping.)

Try to use samples that are -6 dB max. Visually, this means samples that peak at only 1/2 of full scale. Otherwise, turn your layer gain to about .5.

Remove all DC offsets from the sample. In a sample editor, there is usually a line down the center of your sample's waveform. This is the zero-line. The beginning of your sample should be on this line. The end of your sample should also be on this line. However, if your signal is a little above or a little below this line, you will hear a click at the beginning and the end of your sample whenever it is played. If your sample editor doesn't provide any tools to fix a DC Offset problem, you can eliminate the noise by putting a slight fade-in/out at the ends of your sample.

The ADSR will not be longer than your sample. If you have a short sample, it doesn't matter how long you set the attack and delay — the sample will stop playing at the end.

Things change with the sample rate. If you have a really nice setup with all your parameters painstakenly tweaked... things will change if you change the sample rate of your audio card. Many of Hydrogens internal settings and parameters are done based on how many samples go by, and not on how many seconds go by. The sort of things that change are: anything time-base (like attack and release) and anything frequency based (like the cutoff frequency).