MIDI Sequencers

Written by: Karapet Melik-Barkhudarov on 3rd March 2010

MIDI Sequencers

MIDI Sequencers | read this item

March 3, 2010 -- Sound Development and MIDI (0)
March 30, 2010 -- THE MAIN APPROACHES TO MIXING (0)
March 3, 2010 -- The Perfect Mix (0)
January 9, 2010 -- Sound recording and reproduction (0)
January 9, 2010 -- Different professional branches (0)

MIDI Sequencers (i.e., Sonar, Logic, Cubase) work by recording these NOTE ON/OFF events along a timing grid that can be played back at any tempo. When you press Play on a sequencer, it simply sends the data back to the synth, which turns on the notes and plays it just like a player piano. Get it? Because the Synth receives the exact same events that it sent when you played the track, it sounds exactly the same. If it doesn’t sound like you want you can edit it on the screen. That is how MIDI data is converted to sound. Once the synth is playing back a midi track, now you can record that track as an audio track, assuming you have a hardware MIDI synth, by connecting the analog outputs of the synth to the soundcard line inputs and pressing record. Now you have an audio track. Makes sense so far? Cool. If not, read that paragraph again. It’s critical.

MIDI devices (i.e., keyboards, hardware sound modules and control surfaces) typically have 16 channels they can send and receive on. Much like your TV, you can have a different program on each channel. The only difference is that MIDI can play all 16 channels at the same time. These channels correspond to tracks in your sequencer. On each track, you can assign a different instrument. A typical starter MIDI keyboard may have hundreds of instruments to choose from. You record each track while the previous tracks play back. Because MIDI has 16 channels, you can have 16 instruments playing together, like a 16 piece band, if you want, that is totally of your own design.

MIDI IN, Out and Thru (Standard MIDI jacks)

Why is MIDI confusing? Because the terms change depending on your vantage point. From the vantage point of the computer, the MIDI out goes to a device, like a keyboard. The MIDI in comes from a device, like a keyboard or drum controller.

From the standpoint of the keyboard, the MIDI out goes to a computer or another device. When you play notes on the keyboard, data goes out the MIDI out of the keyboard. It does not go through the MIDI Thru.

Keyboard MIDI OUT——–>Computer MIDI IN
Computer MIDI OUT——–>Keyboard MIDI IN
Keyboard MIDI Thru——->exact copy of the data coming in the keyboard MIDI in

The Computer MIDI out passes through the Keyboard’s MIDI IN and then to the Thru. The data coming out the keyboard MIDI thru jack is exactly the same as that which arrived at the MIDI in from the computer. However, and here it gets tricky, the data going out the MIDI out of the keyboard does NOT go through the MIDI thru. Only data coming into the keyboard goes out the thru. Got it? If you understand that simple point you will be ahead of most people. Whew!

USB MIDI

USB MIDI i/o is simpler to deal with from a conceptual point of view. Data flows in both directions down a single cable.

MIDI PORTS: How we get MIDI data into and out of the computer

There are 16 channels for every hardware MIDI IN and OUT PORT (MIDI i/o) on your computer. Your computer’s soundcard may have MIDI i/o, and if not you can buy a MIDI interface to add MIDI i/o. First lets look at all the ways you can get MIDI data to your computer.

Going IN to the Recording Software: 5 ways

MIDI IN Ports: There are 5 basic ways to bring MIDI data into a computer. You need to have at least one of them to connect a keyboard or controller.

1. Some keyboards (not all!) come with built-in USB MIDI interfaces. For these you just connect the USB cable to the computer and install a driver (if required). The port will show up in your software.

4. Various MIDI Cable Conversion Interfaces. There are conversion cables that, along with device drivers, can turn various connectors on PCs to MIDI ports. There are basically 2 types. 1. The Joystick port to MIDI cable (These are primarily for soundblaster soundcards), 2. The serial port to MIDI cable. These cable devices are typically only as reliable as the drivers. You want to make sure they are compatible with your operating system. While these are often inexpensive they may have an issue with your system. If you have to go cheap, go with a USB to MIDI cable like an Emu X-MIDI or M-audio MIDI sport UNO

5. There are a lot of older rack midi interfaces. With these you must be very careful, especially if they were designed for Windows 95, 98 and for older DOS based computers. These typically connect by serial or parallel ports. Steer clear. Without a functioning driver, these midi interfaces will not work.

If you have a number of midi input devices like keyboards, drum machines, controllers and control surfaces they each need a way to connect to the computer. You can have a USB keyboard, a drum machine connected through a MIDI port and a control surface connected by a 2nd midi port and all 3 will input data simultaneously to the track you are recording. Methods can be mixed an matched. You computer will see and use all MIDI inputs connected, whether they are on your soundcard or interface, are connected through your USB hub, or are coming from a separate MIDI interface.

To send control events, (i.e., “notes”) to your sequencer any keyboard with a MIDI out will work, even if it sounds like crap. Remember, you only need it to trigger the NOTE ON NOTE OFF event to the sequencer, which will send them to your available synths, which will send the sound to the speakers. Get it? Though the playing happened at the keyboard, the sound can be triggered at any MIDI sound source, whether they exist in hardware or software. You can even use an old CASIO with the speakers ripped out as long as it has a MIDI out.

To Review: External MIDI IN ports bring MIDI data from outside to inside the computer, where it can be recorded, and sent back out the MIDI OUT port to the external device upon playback.

Going OUT of the Recording Software to hardware and software synths

Now lets look at how MIDI data leaves the sequencer application in the computer and goes to different devices that make sound, both inside and outside the computer.

External Ports: The recorded data goes out of the sequencer to the MIDI out port which is connected to the MIDI in port on your hardware instruments. The obvious example here is the computer that sends MIDI data back to a hardware synthesizer. The instrument receives the data and plays the sound.

Virtual Ports: Internal MIDI ports direct data to sound sources inside your computer. Your sequencer can create a virtual MIDI OUT port for every software synthesizer on your system. Up to 16 MIDI channels can be available for this virtual port, though a typical softsynth may not use them all. An internal virtual MIDI port may also go to a MIDI synthesizer that is built into your soundcard (Soundblaster cards have these) or to a small software synth installed in your operating system, such as the Microsoft GS Wavetable SW Synth, which is part of Windows XP.

Connecting Keyboards and Modules: The sequencer MIDI out port can connect back to your keyboard’s MIDI IN and play up to 16 channels of voices if the keyboard is “multi-timbral” (meaning it can sound many instruments at once). Some synths are not. Old keyboards, like a DX7, only respond to 1 channel unless you hot rod it. You can usually set the keyboard to respond to only one channel if you want or to only channels 1,2,3,7,8, for example, or to all 16. Turning off channels allows you to daisy chain more keyboards or modules by cabling up the 2nd machine from the MIDI THRU on the 1st machine (which is an exact copy of the data coming in the MIDI IN) to the MIDI IN of the second machine. It is possible to have one MIDI port to control 16 different keyboards if you want it too! Usually, if your rig gets this large you will buy a MIDI interface with 4 ports so you can play all 16 channels of your Triton on one port. On a second port you might have with 10 channels from your Proteus 2000, a couple for your Electribe, one for each of your 3 effects box, and the last for your drum machine. Port 3 may use all 16 channels for a control surface and Port 4 might use all 16 more for a digital mixer…ooops sorry, I forgot we are just getting started.

Topics: Audio science, Midi, MIDI Sequencers