Metamorphosis Of A Four Track.
The Trials and Tribulations of digitizing four track analog audio cassettes.

After moving to London from my hometown of Leeds in 1985 I started recording the music that would become the album Granbretan. I used a Fostex X-15 Multitracker tape recorder, a quick and easy way of getting ideas down quickly. With its two inputs, tone and tape transport controls you could record a decent sounding demo.

The music I was recording was instrumental, using a Roland a Juno 106 and an Ensoniq Mirage sampler that was also capable of recording and playing back real-time sequences, as opposed to step-sequences that were programmed note by note.

I later added a Roland JX-8P and an Akai S900 sampler to the mix and upgraded the X-15 to an X-18 that allowed me to have all four instruments plugged in at once instead of just two, however I was still limited to recording only two tracks at a time.

As the touring schedule of the band I was in increased I spent less and less time working on music and more time on the road, in rehearsals or doing other band related things, so my moments alone with the 4-track became fewer and further between. Around this time I moved to a new flat that had a spare room so I could keep all the equipment set up and record whenever I had some free time. I was there for about a year during which time the band split up. I never considered joining another band, deciding instead to continue recording music with a view towards releasing a solo album. Around a year later I sold everything and moved to Seattle.

Seattle, USA, 1991.

Two years after arriving in Seattle I bought an Emax II sampler that had a digital recorder built in, and a Roland Juno 106 to replace the one I sold before leaving England. I was able to a song within the Emax and then record it to two tracks of a 4-track tape then recorded more tracks onto the remaining two tracks. I enjoyed creating music within the Emax but it was a little too sterile for me and I soon reverted back to recording directly to tape.

I recorded music to five more cassettes and also made a video using a VHS based editing system. I was all set for buying some studio time and either re-recording the parts or at least copying the tapes to multitrack and mixing them that way, but all of a sudden something called the world wide web came along that soon had my undivided attention.

World Wide Web

My first computer was a Mac II that I initially purchased to access the web, but soon realized the computer would also be a great way for me to mix the music on my cassettes. The first music software I used was Opcode's Studio Vision Pro and although the process of recording the audio from the 4-track into the computer seemed straightforward to begin with, I finally gave up trying to connect it to my outboard gear and focussed increasingly on using the computer to actually create the sounds, in much the same way as I had used the Emax II.

I soon upgraded to a Power Macintosh 7300 that was able to run much more poweful software, but it just wasn't working for me on several levels. I did have fun with Propellerhead's Reason when it came out, but other than that I was increasingly interested in using the computer to do anything but make music.

Digital Audio Workstation

Ultimately it took the combination of Mac OS X, Logic Pro, Spectrasonic's Omnisphere and an iMac to get me interested in making music again. The operating system and audio production software was light years ahead of what I had been using before, yet the learning curve was surprisingly shallow. Within six months I felt comfortable enough with the new equipment to start making music again, but the original plan of converting those 4-tracks into a record was never far from my mind, and in the Winter of 2011 I unsealed the box of cassettes and began the process of digital conversion.

Metamorphosis

I already had a stereo cassette deck that I picked up shortly after moving to Seattle and decided to use it to digitize the four track cassettes. Over the entire five or sixe year recording period I had used several machines, some with noise reduction in the form of Dolby B or C, some recorded double speed and others at real time with no noise reduction.

I already had a stereo cassette deck that I picked up shortly after moving to Seattle, it had Dolby B and C noise reduction but wasn't capable of playing tapes back at double speed. I figured I would get around this problem by using a speed correction tool built into Logic that slowed music down. There was also the issue of only being able to play two tracks at the same time from the stereo cassette deck instead of four tracks from the 4-track, but again there was solution within the audio software. I would simply flip the tape when it got to the end, record tracks three and four into the computer backwards and reverse them digitally.

What could possibly go wrong?

You can skip these two paragraphs if you see where this is heading, and just in case you don't I'll try to clarify.

I have a stereo cassette deck that can play two sides of a cassette, Side A and Side B, and even though the cassette actually has four tracks, a left and a right track on Side A and a left and a right track on Side B, it isn't capable of playing all four tracks at the same time in the same direction like a 4-track recorder can do. Instead it plays Side A in one side, producing stereo sounds from it's left and right outputs, then when the tape gets to the end it plays Side B, producing stereo sound again until it gets to the end.

So here I come with my 4-track cassette with four tracks of music all recorded in the same direction and at double speed. I put it into the stereo cassette player, rewind it to the beginning, create two tracks on the computer to record to and press play on the cassette deck. I record around 60 minutes of music (if it's a C60 cassette) then I turn the cassette over, create two more tracks on the computer to record to, press play on the cassette recorder and record tracks three and four into the computer backwards.

After the tape played all the way back to the beginning (end) I have all four tracks recorded into the computer, with tracks one and two playing in the right direction and tracks three and four playing backwards.

All that I needed to do now was digitally reverse tracks three and four so they played in the same direction as tracks one and two and I would be ready to start mixing. To do this I accessed the sample editor which essentially treated each track as one huge sample and reversed it bit by bit.

After several minutes the processing was completed and now I had four tracks all playing in the same direction. After trimming the front of tracks three and four and lining them up so they started at the same time as tracks one and two I was able to play the four tracks as if I was playing them from the audio cassette on a four track recorder.

What went wrong?

At first it sounded great, all four tracks playing in the same direction at the same time, but after only a few minutes tracks three and four started going out of time with tracks one and two. After a few moments thought I put this down to the tape tending to speed up ever so slightly as it played from beginning to end, and even though the audio was now playing in the same direction it was originally recorded into the computer from a tape deck that speeded up the audio slightly each time it was recorded. By reversing tracks three and four I was essentially doubling this effect.

I first tried tempo stretching tracks two and three so they would end up being the same length as tracks one and two, which would theoretically make them play back at exactly the same rate, but still the tracks went out of sync in the middle sections, and the process also generated lots of audio artifacts that dramatically changed the sound.

The only solution was to cut up the audio that was going out of time on tracks three and four and create new tracks where the parts could be copied and moved back into time with the audio on tracks one and two that I left alone. After a couple of hours carefully cutting the audio up into different pieces I had around thirty tracks of audio. Tracks one and two were the same untouched tracks I had originally recorded into the computer from the cassette, and tracks three through thirty were all the different parts from what was originally track three and four.

All that remained to be done was go through and painstakingly nudge each part back into time with the audio on tracks one and two. Some sections on tracks three and four, such as sequenced parts I had originally recorded from the sequence in the Ensoniq Mirage were too long to simply nudge into place, because after a while they would go out of time. In these situations I ended up digitally stretching the section of audio slightly so it would stay in time with what was playing on tracks one and two, and because these sections were relatively short I didn't notice the kind of noise I heard when I had tried stretching the entire tracks.

Many of the sections were easy to realign with the untouched reference tracks on one and two, but most were almost impossible to align with perfect accuracy primarily because the original music was never recorded using a click track. The only musical elements that were ever in time were percussion loops that only appeared briefly on most of the tracks, and long arpeggiated sequences recorded manually into the Ensoniq Mirage and recorded onto a single track for the duration of the entire cassette so I could play other parts to it as it went along.

This whole process of realigning all the cut up sections was often mind numbingly difficult and I began to despair that I would ever get it to sound the way I had originally recorded it. Some sections were pads that faded in and out with no way to sync them up exactly as they were recorded. A slight nudge of a pad section in the wrong diresction would completely alter the feel of the track, essentially destroying it. Finally, after several weeks I had each track sounding as close to how I remembered it as possible.

The next step in the process was to clean up the beginning and end of every cut up section, to minimize the pops and clicks that occur when you slice a sample up into pieces. Some of the sounds faded in from an empty track, and even faded out the same way, so these were easy to fade in and out, but other parts were sliced between different sounds so I had to remove the pops and clicks that were caused by the equipment when a new part was dropped in and out during the recording process.

After all twelve tapes were recorded into the computer, aligned and cleaned up I started mixing.

Most of the mixing work was panning, so the parts sat correctly within the stereo field, adjusting levels and applying effects to parts that needed it. When I originally recorded the music I had various effects in mind for specific parts that I didn't have access to at the time, so that was gratifying to finally be able to realize those goals.

I was also able to make use of the powerful EQ tools within Logic to get the recorded tracks closer to how I originally imagined them but was unable to apply because of the limitiation of the orginal equipment. Throughout this process I was surprissed how easily I was able to hear the original vision in my head and apply it to what I was listening to all these years later.

Finally the songs were ready for mastering, and as much as I would have like to have done this myself I know how important this part of the process really is and luckily I know an excellent mastering engineer who is also a friend, Steve Turnidge.

Steve has actually written a couple of books about mastering, Desktop Mastering and Beyond Mastering published by Hal Leonard, and although I have become somewhat enlightened since reading them I still regard mastering as something best left for someone else to do.

An hour or two after sending Steve the first track I got an email back telling me it was, for all intents and purposes, unusable.

The noise from the cassette tapes was apparently so bad that something would have to be done to the raw tracks before mastering could take place. It was at this point I was introduced to iZotope RX.

For those of you unfamiliar with this amazing software it basically allows you to see the music as if through x-ray glasses, and with photoshop style tools lets you erase parts of the music such as clicks, thumps, crackles and hums in much the same was a graphic artist would process the photo of a model for a magazine cover.

It also has a feature that removes background noise produced by the tape medium itself by taking a sample of the tape noise before the audio kicks in and going through and removing that noise sample from the entire track.

After spending a week or so removing noise and other artifacts it was back to Steve for another shot at mastering.

This time it took several hours before I got an email telling me something weird was going on with the sound, and after looking at the music through his x-ray glasses he noticed I’d gone in and removed all the noise above a certain frequency on every track using the eraser tool I really liked. This bull in a china shop approach to noise reduction turned all the sine waves into square waves and caused all kinds of terrible issues that made the intitial noise issues pale in comparison.

It was at this point it was decided that we would need a 4-track recorder to play all four tracks at the same time into the computer. The process of reversing and slowing down tracks digitally to line everything up may have made sense at one point, but it was becoming clear it was destined to fail for one very simple reason.

Music Bleeds

As soon as one track went even fractionally out of time with an adjoining track there was a small but noticable amount of audio bleed from the adjoining track not going out of time that caused strange artifacts that ended up as the kind of noise that proved impossible to remove.

The only solution was to play back all four tracks at the same time, in the same direction, into the computer so that all four tracks were exactly in time as the rest.

This is where Mike Perez and his PortaStudio came to the rescue.

It turns out Mike's four track recorder not only played back all four tracks at once but it also had a Dolby B and C noise reduction setting that came in very useful because a couple of the tapes used one of these two noise reduction settings during recording. It was also capable of running at twice the normal speed, which is a useful feature when recording because you end up being able to record twice as much information to the tape as you can at normal speed, so you get a higher resolution recording. It also meant that we didn't have to do any digital processing to get the tracks to play back at normal speed.

Steve Turnidge had also recently added a new digital audio interface to his system, so we were also able to record the audio at a higher bit rate than was possible before.

Lights, Camera, Action.

The stage was set to finally turn the analog signals recorded onto iron oxide covered tape over two decades previously into a digital format ready for mixing and mastering.

After each tape were played from beginning to end, and the four separate audio tracks were recorded to four digital tracks on the computer, Steve would then copy them to my removable flash drive and off I'd go back to my studio to import them into Logic Pro X.

I repeated the same process I outlined before, cutting the tracks up into individual sections and moving the parts to new tracks, but this time I didn't move anything out of sync with the rest, instead I was doing it because I'd learned from the first run through that it was not only easier to mix if all the parts were on separate tracks but also easier to apply fades to get rid of the unwanted pops and clicks caused by the original recording process, although I did leave several that I actually liked.

I ended up moving similar types of sounds to the same track, so all the percussion parts, strings and other pads, lead sounds and sound effects would be grouped together on their own tracks.

Within a couple hours of sending the first mix over to Steve I got the mastered version back and was very happy with the result. The original vibrancy was still there but without all the noise and other artifacts.

The project was finally drawing to a conclusion, and within a couple of weeks I had all the tracks mixed, mastered and ready for release.

The process of publishing, distributing and marketing the music is a whole new story that I'll post to my journal in due course, but in the meantime don't let me stop you from heading to the Store to buy a copy of Starship Oak so you can hear for yourself what a 4-track cassette recording sounds like.