This tutorial covers sequencing topics using the Max
seq object. We will cover basic sequence setup, and the ability to start and stop playback. We will also examine a few ways to control the playback speed of a loaded sequence.
MIDI event recording and playback (generally called
sequencing) is an important task for many MIDI-based Max programs. There are several objects within Max that can accomplish MIDI sequencing tasks, but the
seq object provides the easiest interface while still allowing for the recording and playback of notes, controllers and all other MIDI messages.
One of the things that makes MIDI sequencing so useful is that you can change playback speed with little effect on the output sound; the MIDI recipient is responsible for sound creation, and merely responds to the data stream provided by the sequencer. Thus, playback rate change is an important part of MIDI sequencing, and is covered in depth with this tutorial.
Our tutorial patcher contains three regions containing patcher logic routed through a single
seq object. The leftmost area (labeled
1) shows the most basic of MIDI sequencing setups. The
seq object is initialized with a MIDI sequence name as its argument. This sequence is loaded when the patch is opened, and is available for playback. The left output of the
seq object is the playback output – it sends raw MIDI data into a
midiflush object, then to a
midiout object.
The
midiflush object is used to maintain the note-on/note-off pairings of a
raw MIDI stream, and will send note-off messages when it receives a
bang. Using
midiflush, we can stop all sounding notes even if the sequence is only half-way through its playback. Clicking on the
stop message at the top of the patch will not only stop the sequence, but will send a
bang to
midiflush to stop all sounding notes on your synthesizer.
Double-click on the
midiout object and select a valid MIDI output device for your system. Then click on either the
button or the
start message to begin sequence playback from the start of the sequence; the MIDI sequence loaded into the
seq object will play back at its “natural” speed. When the sequence is done playing, a
bang will be sent out the right outlet of the
seq object. We have this connected to a
button object, giving us a visual indication of sequence completion.
Try each of the messages attached to the
seq object, and
stop it during playback to hear the results of the
midiflush object. Also notice that playback always starts at the beginning of the sequence.
The next area (labeled 2) contains a bit of programming that changes the playback speed of the sequence. It is based on the argument to the start message: an integer appended to the start message will change the playback rate. A playback rate of 1024 represents normal speed; hence, 512 is half-speed, and 2048 is double-speed. While this may seem convoluted (in comparison to using a floating-point "rate" from the start), it is easy to calculate the proper value for playback.
In this case, we use a floating-point
number box for playback speed, and multiply it by
1024 to get the number expected by
seq object. The number is stored in an int object; then, hitting the
Go! message box, we trigger a
button that sends the number through a
start message, with the properly formatted message sent to
seq. Remember that, since the
button object converts
any message into a
bang, the text in the
Go! message is arbitrary.
To test this, change the floating-point
number box to
0.5and hit
Go!. Change it to
2.0 and hit
Go! again. You will hear the sequence play at the suggested speed. Using an argument to the
start message is an easy way to control playback, but this method can only be used to change playback speed at the start of playback. To change the rate
during playback, you need to work with the
tick message.
The rightmost area (labeled
3) shows how to change the speed of the sequence
during playback. Two messages are responsible for this: a variation on the
start message (with the argument of
-1) and the
tick message. The
seq object has an internal timer that is used by default for playback. However, when the
start message has the
-1 argument, the transport of the
seq object is disengaged from an internal clock and depends on incoming
tick messages to advance the sequence.
In our example, we are using a
tempo object to transform a
bpm (beats per minute) value into the appropriate ticks. The arguments to
tempo set a default
rate (in this case,
120 bpm), a default beat
multiplier (
1) and the number of pulses for each whole note (
96, the equivalent of
24 pulses per quarter note). If you click on the
start -1 message and then turn on the
tempo object with the
toggle box, you will hear the sequence play back at
120 bpm. Next, change the tempo to something faster (say
200 bpm) with the
number box connected to its second inlet; if you restart the sequence you will hear it play much more quickly. Turn the
tempo object's speed down (to
50 bpm) and you will hear very slow playback. You can also change the
tempo object while the sequence is playing, and the playback will change to match your selected speed.
There are many creative options when using the
tick message for playback clocking. Using a
line object to alter the
tempo object would allow you to ramp up playback speed for the duration of the sequence; alternatively, you could create an curve that would cause the playback speed to wobble while it plays. You can also
stop the
tempo object (using the checkbox) to temporarily pause playback – when you start it again, playback continues from the point at which you stopped. Using your own clocking provides much more flexibility than simply changing the arguments to the
start message.
The
seq object is a robust sequencing tool, allowing you to play back MIDI sequences at a variety of speeds. This is especially true when you override the internal clock and use the
tick message to alter playback in real time. The output of the
seq object should be routed through the
midiflush object, so that stopping playback will also stop any currently sounding notes. The
seq object is perfect for playback of short loops, note/controller phrases or even complete sequences.
See Also
Name |
Description |
seq |
Sequencer for recording and playing MIDI data
|
midiflush |
Send note-offs for hanging note-ons in raw MIDI data
|
tempo |
Output numbers at a metronomic tempo
|