Technical Details of the 1970s LHS Audio Project
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  Instructions   Technical     Updated 2022-01-23
Table of Contents
  • Where Did These Recordings Come From?
    Comments on Audio Quality
  • Requesting Compressed Digital Audio Files (MP3, SHN, FLAC)
  • Sharing Your 1970s Analog Recordings
         Cassettes and Vinyl Albums
  • Sharing Your 1970s Digital (CD) Recordings
  • Why CD Ripping and Copying is Error-prone
  • Error-free Ripping and Copying of CDs
  • Disk-At-Once versus Track-At-Once
  • Lossy Compression Formats (MP3)
  • Lossless compression formats (SHN and FLAC)
Where Did These Recordings Come From?

If an event is not in the list of recordings, I probably don't have a recording or I haven't digitized it, yet. Not all events were recorded back in the day, and the school has no archive. In a few cases, due to my record-keeping, I have digital recordings that are not yet in the list. It's always OK to ask.

Following the 2005 reunion of 1970s LHS music and drama alumni, I began collecting recordings from that decade. I have been digitizing these cassettes and vinyl albums for the purpose of burning CDs, and I have over 40 hours of audio on my hard drive. Some events were professionally recorded (mostly by Director Recording Services) and some were recorded on consumer-level equipment (usually battery operated cassette recorders operated by students and parents). Most of the recordings are quite listenable, even if they aren't studio-quality recordings.

I am happy to share these recordings.

I can provide MP3s or standard audio CDs.

None of the LHS recordings are of modern, studio quality. None were originally produced for CDs, and all original source material is from the 1970s. However, most of the material is good enough to be worth the effort. The best quality items were professionally recorded and distributed on vinyl; there may be a few pops and scratches, but the vinyl held up and played back well.

Many factors affect today's playback quality. Microphone placement, audience interruptions, attempts by the taper to save tape by turning the recorder on and off, and equipment quality (original and playback) come back to haunt us. Over time, cassette tapes stretch slightly, resulting in an inconsistent transport speed across the tape heads and a warbly sound. In defense of those who did the recording, high school concerts are difficult to tape because the volume levels vary wildly from moment to moment. Playback quality varies with each tape, and may vary during a tape. In particular, the jazz/rock concerts made heavy use of drum sets and bass guitars, and these rumbling sounds caused varying degrees of audio problems. Most of the recordings are pleasantly listenable, and there are a few miraculously good recordings of important events.

I have not used any software to remove pops and hiss. There is a lot of source material, and I spend about three times the length of any event to eventually get the digital files into CD-ready form, including initial hard drive transfer, track separatation, paper insert preparation, etc. The use of audio enhancement software would increase this time. If you want to improve the audio, rip my CDs and knock yourself out.

By the way, if you decide to enhance the audio or copy the CDs for further distribution, I encourage you to use error-free ripping techniques, such as with EAC (Exact Audio Copy). Off-the-shelf CD copying software does not do a perfect job of this. Ask me about EAC.

Compressed digital audio files (MP3, SHN, FLAC)

I can provide download links for MP3 files.

I back up my audio files in SHN format. This is a lossless, compressed audio format that predates FLAC format. MP3 is compressed, but it is lossy. MP3 files result in noticeably lower quality audio than the original CDs, but SHN and FLAC can be decompressed into the original CD-quality files.
I can send SHN files on a data disk instead of audio CDs. I can create FLAC files, but I have been trading audio for a long time and I normally use SHN. Discuss this with me by email and if you really want FLAC, we'll figure something out.

Sharing Your 1970s Analog Recordings
Cassettes and vinyl albums

If you have recordings that I don't have, I can transfer tapes or albums to digital files.

Please send me the original analog items. Don't copy a cassette or album onto another cassette for me, because the audio quality will degrade. If you want to copy onto a second cassette to guard against shipping damage, that's a good idea (but send me the originals and I'll return them).

If you live in New York State, contact me to see if I'll be in your area in the near future and we can exchange items in person.

Sharing Your 1970s Digital (CD) Recordings
I encourage you to send me any recordings not in my list, including recordings that are already transferred to CD. Please conform to careful copying techniques. If you're not careful, multi-generation copies of CDs can acquire errors. Careful copying techniques are not obvious. I can help.
Why CD Ripping and Copying is Error-prone

I am not exactly an audio expert, but I can pass along some information. The "Orange Book" describes the properties of compact disks and the way audio data is laid out on CDs. Commercial CDs and CDs burned on your PC conform to Orange Book standards. The Orange Book does not apply to non-audio data CDs. The word "burn" reflects the process by which a laser beam inside your CD-drive is fired at the disk in order to set the audio data that can later be read (by another laser beam) during audio playback.

The word "rip" refers to the process by which digital data is extracted from a CD and saved on a hard drive or other disk.

Mass-produced, factory CDs use different equipment and software than your PC, and sometimes you'll encounter an audio CD burned on a PC that doesn't play on some players. However, today's new players rarely have trouble with CDs burned on today's PCs using today's software.

A CD player, even a typical stereo component, has computer-like circuits that operate the laser, read the data from the disk, and convert the data into audible sounds for your speakers. This is analagous to the stylus of your old turntable that played vinyl albums. Technically, an important difference between albums and CDs is that the audio "information" on an album is laid out in a continuous (analog) stream, while the information on a CD is laid out as discrete (digital) bits. The bits can be assimilated and played back so closely together, though, that the human ear doesn't notice the difference. Cassettes are also analog in nature; the information is saved continuously on the magnetic tape.

The analog information on an album or tape can only be stored on its specific sort of media. In order to transfer the information to a hard drive, the analog media must be played in real time and re-recorded. By real time, I mean that it takes an hour to re-record a one-hour concert. The information on a digital CD can be extracted without actually playing it, for other media such as a PC hard drive. A whole CD can be copied within a few minutes or less.

When an album is scratched, the continuous stream is interrupted and you hear a pop as the stylus tries to "read" the stream. If you look closely at a CD, you'll probably see some scratches, but you won't hear them. The circuitry in the player corrects for small errors and plays back the sounds so that your ears don't hear the problems. Of course, this correction process is not infallible, and it is certainly possible to damage a CD so badly that it can't be played, and you've all probably encountered bad CDs, but they are unusual.

The process of copying a CD is much like the process of playing it back, although the copy can be made more quickly. The implication is that the copying process corrects for errors. The usual consumer CD copying software ALWAYS does some correction, and this means that a copy of a CD is almost never EXACTLY the same as the original. You probably won't hear the difference, but deep down in those digital bits, there are differences.

A problem occurs when you have a CD such as an LHS concert, and we alumni make copies of copies of copies for our friends. If every generation is a little different, eventually someone gets a copy that SOUNDS different, because the correction software is too lazy to perfect each generation. However, there is free consumer software that is able to guarantee an exact copy every time, but it's not well known outside the bootleg trading community.

Error-free Ripping and Copying of CDs

The usual CD copying software that comes with your CD drive (Windows, Roxio, Nero, etc.) works fine for data disks, but allows for errors on audio disks in accordance with Orange Book standards. In order to guarantee error-free rips, you must install additional software. Fortunately, there is freeware with a small footprint, i.e., it only runs when you want it to and it's easy to uninstall. This software is called Exact Audio Copy (EAC) by Andre Wiethoff. This software is not exactly a novice-level application, but it solves the problem of propagating errors over many generations of CD copies.

EAC performs multiple rips of each CD track and compares each rip, byte by byte, to ensure that each rip is the same. If so, the rip succeeds and the corresponding WAV files are saved onto the hard drive. Damaged disks can result in rips that are not guaranteed to be error free. EAC can be used to rip bad tracks, with the caveat that the resulting WAV file is not an exact duplicate of the CD data (because the CD data can't be accurately read).

By the way, there is no need for "error free burning". When burning a CD, the data in the source WAV files is always burned exactly onto the disk without anything analagous to error correction. Aside from outright hardware failures, the only time we're concerned about error correction is when ripping (extracting) music FROM an audio CD.

Disk-At-Once versus Track-At-Once

Many of the LHS event recordings were made without turning the recorder on and off, so there is a continuous stream of sound for 30 minutes or more. However, within that continuous stream, there may be many separable sections, i.e., different musical pieces, play scenes, etc. Once the unbroken recording is on a hard drive, it can be split into sections that will later become tracks on a CD.

It is partcularly useful in these modern times to separate long recordings into multiple short tracks because the tracks can be downloaded to a phone or other MP3 player. Users of portables may not want a whole concert or may have difficulties with very long tracks.

On the other hand, home listeners may find it fun to turn out the lights and relive a concert in one long chunk, with all the applause and comments from the stage, and without breaks of silence between pieces.

All disk-burning software can burn audio CDs in either of two modes: disk-at-once (DAO) or track-at-once (TAO). DAO burns the disk with no silence between tracks, while TAO burns the disk with a silent block (usually 2 seconds) between each track.

When you listen to a DAO CD, you can watch your player change the track numbers, but you won't hear breaks. If the tracks are sections of a longer recording, the audio will sound like one long recording as long (as the tracks were laid out in the correct order). Users can rip each track individually for a phone.

Sometimes, with events like an LHS concert, a recording will have some long sections and some short sections. So, you might want silence between some tracks, and no silence between others. In this situation, insert silent blocks into the appropriate tracks using a WAV file editor, i.e., the same editor that you used to separate the tracks. Then burn the disk DAO.

The only time to burn TAO is when every track is truly separate and should be laid out with intervening silence.

If someone gives you a TAO disk that actually has continuous audio, you can rip the tracks and re-burn the CD DAO.

Once in a while, you'll encounter micro-gaps on a DAO CD. These are very short silent gaps between tracks, usually just a few milliseconds, but they are audible. With a WAV editor, you will see the silence in the tracks, and the silence can be edited out and reburned.

Lossy Compression Formats (MP3)

MP3 files are small because certain frequencies and other data is removed, but this data removal causes audible differences. For this reason, MP3 is called a "lossy" compression format. This is sort of like the difference between a CD and FM radio. FM sounds OK, but it's not as good as a CD.

MP3 files can be converted to WAV files, but the stripped data cannot be recreated. It's like cutting a 5x7 photo to make it fit in a 4x6 frame. If you later decide to put it in a 5x7 frame, the edges of the photo are gone. The clipped photo will fit in a big frame, but it will look silly.

If you have an audio CD, it was originally burned with WAV files. WAV files are big and uncompressed, but they contain all the frequencies and such. It's OK to rip that into MP3 files for a phone, but don't do that for me. Send me the actual audio CD (or an error-free copy so that I can rip the WAV files myself.

I use MP3 for my phone or for saving bits of audio on my web site. I use EAC to "encode" the audio files from WAV to MP3 (a free "Lame" CODEC can be plugged into EAC). The word "encode" is used to refer to the conversion from uncompressed WAV to some other format (using a Compressor-Decompressor, or CODEC). "Lame" is the author of EAC's MP3 CODEC plug-in.

Lossless Compression Formats (SHN and FLAC)

There are two common "lossless" compression formats for audio files, Shorten (SHN) and Free Lossless Audio Codec (FLAC). For historical reasons, I use SHN to back up my bootleg library, although FLAC is more common today. WAV can be converted to SHN and FLAC without losing any audio data (hence the term "lossless"), and SHN and FLAC can be converted back to WAV in order to burn a CD. I use a program called Traders Little Helper to perform these conversions.

If you want to make files available for download on the interet, use FLAC. The files are smaller and it's more common these days. But they're still not all that small, so you'll need a lot of space on your server. A full, 80-minute CD is about half a gigabyte even when compressed.

I would be happy to provide you with data disks containing compressed SHN or FLAC files (preferably SHN since I already save those, but talk to me). In the hardcore bootlegger world, some traders concern themselves with whether their source of compressed audio is a copy of the ORIGINAL compressed file, rather than a secondary rip-and-compress. My opinion is that this concern is moot. There can be differences in word boundaries at the lowest data levels, but these differences do not affect the audio as long as the rips are error free. So, if you want to use EAC to rip my audio and then compress to FLAC for sharing on an internet site, knock yourself out.

In these modern days of digital recorders that can upload to a hard drive, there are arguments for sharing data files rather than as audio that will be ripped and shared again as audio CDs. However, the LHS audio all comes originally from vinyl and cassettes, so again, it's a moot point. Careful copying techniques will cause no audible differences between copy generations.