Audio Class

Audio - analog data processed into a speaker

Up to this point everything has been about digital MIDI data streams in and out of computer circuits, but that's not sound. Now we look for where the sound comes from. Any equipment that generates sounds from MIDI data has circuits inside that use the MIDI data to activate tone generators usually one for each note. If you play a four note chord on its keyboard entry system in the right hand and three more notes in the left hand , you would need at least 7 circuits that can generate tones. You can see that the modern synthesizer or electronic piano or even a drum machines have a lot of multiple circuits inside to do this job. The net result is analog signals or sound coming out of a different port than the digital commands going in. The analog sound is probably in stereo as well. More circuits. Add internal sound effects - probably to generate a stereo output easily, and you have something our ears can hear. Some equipment have multiple audio output jacks, others mix the output of the tone generators internally to a stereo image and have left and right audio jacks. The point is: digital serial data going into a device on its own port, and analog sound coming out on its own ports.

Mixers

We are about a third of the way to the speakers. Still no sound, but we'll get there. All of these sound sources, especially if you are a gear head and have a gazillion synthesizers stacked up, create a lot of audio channels or inputs into a mixer. Its job is to sum all this analog information into a reasonable set of outputs. To some that means matching the number of tracks on a DAT tape recorder or studio recorder or maybe just a stereo pair going to a PA system. Somewhere we need a mixer to handle all the analog signals.

Mixing can be done inside a computer as well. First we will have to convert the analog information back into a digital form and use software to model what happens when different analog signals get mixed. That is a hairy mathematical process that has taken many years to perfect, but is very common place with the computing power of the modern desk top computer. Or we can do the job externally in a box with a lot of knobs to control the audio inputs and sum them into a manageable set of audio outputs. This is the common way to handle live bands or any situation that a house PA system is going to be the main sound source.

Computer Sound

When you connect analog signals to a computer you need to go through a plug-in card that converts the analog to digital or an A/D converter. This takes the smooth varying analog signal an chops into many levels that are each given a number value. Now the computer can understand how to represent the data coming in. Conversely, a D/A converter goes the other way. This type of circuit is usually found on the same sound card. It is useful to hear what is being recorded by software in the computer or to play other channels from a session such as monitor channels that players can hear while inputing their sound into the computer. Mixers do the same thing externally. This is what is called a submix. You can have a prerecorded mix of say drums, piano and bass delivered to headsets or monitor speakers, then the players can contribute new parts to the recording at the main mix. The total sound can then be sent to a PA system or back to the recording device. Obviously mixing can get complex. It is an art-form in itself. Go into a music store selling audio gear and pick up a Mackie mixer brochure. They show pictures and provide descriptions of dozens of ways to hook up mixers to get the job done.

Software

Early in the game all the various jobs musicians wanted done, we accomplished by different software. Now modern sequencing programs manage all the various types of data. There are separate tracks for analog signals and MIDI data. There are subroutines that take care of effects and mixing. There are also programs that model synthesizers so that everything can be done inside the computer and no outside boxes need to be used at all. If you want to add live sounds, then you have to start plugging in circuit cards.

The software's audio product is a .wav file-type that can be read by CD burners. The MIDI data is stored on a hard drive as a normal data file. You can also store System Exclusive data as a normal data file.

Recording the Masterpiece

If you have a CD burner as part of your computer rig, then recording your songs complete with all the bells and whistles of added instruments and effects, is a snap. The sequencing software provides a file of many types, but the .wav is what the CD burner is looking for. CD burning software in now employed to do the job. Most desk top computers come with such a program. Cakewalk sells their version called Pyro. Check the music magazines and see the latest offerings, then seek out a demo at a equipment music store. At this level they usually have "Pro" in their title somewhere.

That's a Wrap

Given enough money, you can set up a fine recording studio with the ability to have stunning results available on a CD. That use to be a $20,000 to $50,000 proposition not too many years ago. Now it is much less to get started. When you stop spending, is up to you. So start saving part of your earnings to invest in a home studio, if you want to be musically creative. Life is too short to go the route of writing out parts by hand, hiring musicians to do fill work, and having a band of professional musicians to grind out your tune, and a studio to play all this in, scheduled by the hour. Please! A few thousand dollars and you can do it all. Well, a few thousand more for a killer computer.

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