Creating Music Loops

Much like tiles for the background of a Web page or those in a tile-based world, a music or audio loop is an economical means of creating a larger sound or musical idea from a smaller one. The goal is to make the loop seamless and interesting. In most cases, there should not be any sense of beginning or end to your sound because this very quickly creates monotony. Looping sound has been in use since the early days of electronic music and musique concrète (a form developed in the early 1940s, based on the recording, mixing, and synthesizing of sounds found in nature). In the old days, loops were created by splicing the ends of a tape-recorded sound and piecing the start and end segments of the sound together with splicing tape. This looked like you guessed it a loop. The sound designer would then set the looped tape on the reel-to-reel and hit the Play button, and there you had your repeated sound. Needless to say, this was a very time-consuming process, and any mistakes made in the cutting of the tape were very difficult to repair. Add to this the fact that there was no way to determine exactly where to cut the tape except by trial and error with a piece of chalk to mark potential cutting points.

Thanks to the awesome help of computers, this process has been made much easier, faster, and precise beyond aural perception. In digital audio the basic process is still the same as it was with tape, only we now have the ability to "audition" the loops before making the cut, and of course there's the magical Undo button. I will discuss two ways of making looped sounds on the computer: The first one is with beat-/loop-creation soft and the other is by editing preexisting sound and music with digital-audio editing software.

Drum Loops

Drum loops are popular in games and on Web sites right now. The style is derived from electronic dance music that's been trendy since the '90s. It is also the basis of most rap and hip-hop music. For people who are not necessarily musically inclined, drum loops are really the best means of adding a sense of action to anything happening on the screen. The typical drum loop features three things:

1. A repeated rhythmic drum pattern

2. A complementary bass line

3. Miscellaneous additional atmospheric sounds, such as ambient synthesized orchestral strings

There are dozens, if not hundreds, of programs out there on the Internet for beat and loop creation. It is standard for these programs to open up to a default groove, which you can then edit to your liking. (Just don't use the default one in your game without changing it significantly first!) You can just open up the software and make a few adjustments to the default groove to create your beat. The start and end timing of the loop will already be set up when you save the sound from the program, and all you'll have to do is optimize it for Flash (more on this later).

My favorite software for beat creation is ReBirth (Propellerhead Software; www.propellerheads.se). It is very easy to learn and seamlessly sets up your beat, and you simply save. The coolest thing about ReBirth is that it has "mods." Mods are essentially skins for the drum machine. But not just graphical skins these skins change the entire sound. You can instantly change the beat you just created from a driving rock sound to a jungle texture to anything else, just by changing the mod. The sounds change, but your beat remains intact. At first this program may look overwhelming, but the cool thing is that the beats are already set up when you open the program, and literally all you have to do is click a couple of buttons of your choice and the beat is now your own. If this is not easy enough for you, there is a Randomize Pattern button in the menu that automatically reorganizes the beat.

The downside of ReBirth is its very high price. The Propellerheads make a smaller, less functional version, called ReBirth One, which is a little more accessible.

There are demo versions of these products on the Web sites, so you can try them out and see if they fit your needs.

A list of popular (and more affordable) drum machines is included in Appendix E,"Developer Resources."

Editing and Preparing Audio Loops

Before importing your audio file into Flash, it will most likely need to be prepared. Much as when preparing a GIF or JPEG graphics file, there are many adjustments that should be made with audio, the most important of which is file compression. Flash is capable of compressing the audio file for you, but in many scenarios it is best to set up the compression before bringing the file into Flash so you can get the desired sound-quality-to-file-size ratio. There are countless audio-editing programs available. The professional standard is Sound Forge (Sonic Foundry; www.sonicfoundry.com), but the one that many non-musical audio types use is Cool Edit (Syntrillium Software; www.syntrillium.com). If you can get a used copy of Sound Forge version 4 or later for a good price, do it, because it is far more powerful than Cool Edit.

Here's a basic checklist to use in preparing your audio for Flash or any other Internet use. Of course it's just a starting point, but it will give you some pretty good ideas and reminders.

1. Length (2.5 seconds, for example).

2. Volume (overall, as close to 0 dB as possible not too loud, not too soft).

3. Dynamics (moment-to-moment volume level should be consistent).

   This is the most common rookie oversight! Don't taunt your listeners with 2 seconds of quiet violin sounds and then blast them with a crash cymbal. They will hate you, and you might as well put your entire project on a neon-yellow background with white writing.

4. Sample rate and bit depth (22 kHz/8-bit, 44.1 kHz/16-bit, and so on).

   The sample rate is a representation of how many times per second a sound is sampled for digital storage (just like the frame rate for video or animation). A sound sampled at 8 kHz will take up less memory than a 44.1 kHz sound but will be much noisier. Bit depth represents the chunk of numbers used to describe each sample. Eight-bit sound files take up less space than 16-bit but don't sound as good. For reference, CDs are 44.1 kHz and 16-bit. If you can sample your sound file at 44.1 kHz/16-bit without it becoming too large for your Flash project, by all means do so.

5. File type (WAV, AIFF, or MP3).

   These are the recommended file formats for Internet use. The WAV and AIFF formats are uncompressed. The MP3 format is compressed, with a small amount of loss in audio quality.

To simplify the choices and numbers in items 4 and 5 above, the smallest file size with the poorest sound quality would be an MP3 at 8 bits and 11 kHz, whereas the largest file size would be a WAV or AIFF at 16 bits or more and a sample rate of 44.1 kHz or more, and would have superior sound quality.

Audio editors like Cool Edit and Sound Forge allow you to edit your sound files graphically. On the next page you'll see the "dashboards" of Cool Edit and Sound Forge. A cursory study of these interfaces will show you their essentials.

The straightforward interface of Sound Forge actually allows you the most sophisticated controls around.

Cool Edit Pro also offers you many ways to control and manipulate any sounds.

As you can see from these images, both programs allow for extremely precise editing of the sound data. When checking the length of the data (item No. 1 above), keep in mind that you must check your loop to make sure it's continuous and clean. Both Cool Edit and Sound Forge allow you to loop playback so that you can test the length for proper fit. There is really no way to ensure that your loop will be seamless except by good old-fashioned trial and error. However, I can give you a couple of tips. First, listen carefully to the very beginning and very end of the loop. How does the end work? Does it lead up to the beginning hit? Does the ending fade out? Is that what you wanted? If the sound is repetitive throughout (for example, "Boom boom bap, boom boom bap, boom boom bap"), you will be able to see that very easily on the editing screen. Take note of the timing (in seconds, tenths of seconds, and so on). Zoom in to make sure that the sound ends exactly before the next hit, and adjust as necessary. (You don't want it to be "Boom boom bap, boom boom bap, boom boom b .") There are options for processing the sound to make it louder or softer, to pan left or right, and more. These programs allow you to adjust the sample rate and bit depth right there on screen, but you can also use the Save As command and choose the sample rate and bit depth there.

You can see a list of popular audio-editing software in Appendix E.

Sound is a very important part of a game. In this chapter we have outlined several reasons why you should give sounds a lot of attention when developing your games. Hopefully you will take the time to look for or create sounds that fit well with your game.