Article written by Notable on the Virtual Guitar project

The Virtual Guitar: Rockin' the CD-ROM World
By Daniel C. Cantor and Mark Weltner

The Virtual Guitar is a new interactive CD-ROM game that is an air-guitarist's dream-come-true. The game begins with your descent from the heavens, listening to Lloyd, an old guitar master and your guide, as he waxes poetic, reminiscing: "That's the way it went down, man. I was trying to get that sound --  the sound that would take my guitar to another place. But something went wrong -- very wrong. The surge I created that night blew out every fuse in West Feedback and zapped me up here into the Stratosphere. But hey -- at first I dug it: no sleazy club owners. But you know, I never knew how much I'd miss it...  My town, man, my town. No better place for a guitarist to cut his teeth. If you haven't got your sound together, there's no mercy. But if you wail -- you can really rise above."

[Color slide: Downtown, West Feedback]

After making the trip from the stratosphere, through the clouds, above the West Feedback city skyline, you land in your bedroom. A CD player appears on the screen and you choose Whipping Post from the song list. Picking up your Virtual Guitar, you get ready to play. Although the Virtual Guitar looks and feels like a real electric guitar, it doesnt have any frets, and the strings do not extend down the neck for that matter. There's no need to memorize any notes or chords; you simply focus on which strings to pluck or strum, and when. The challenge is to strum the strings with the right rhythm and beat, or to match the lead, and carry the melody.

[Color slide: The Virtual Guitar]

What we just described comes from the first PC-based CD-ROM title based on virtual music technology developed by Ahead, Inc. of Bedford, MA. Notable Productions (Mark Weltner and Daniel C. Cantor) of Watertown, MA, was hired as by Ahead as musical producer and consultant for the Virtual Guitar project. This project tested our abilities in numerous ways -- in production, composition, performance, musicology, technical ability and stamina. One of our first responsibilities included assisting Ahead in selecting appropriate songs and artists. These include songs originally recorded by Aerosmith, Gin Blossoms, Motley Cre, Soul Asylum and BioHazard to name a few.

Next, we began arranging shortened versions of the songs. The reasoning behind this was  due inpart to the limited memory of a CD-ROM. Much of the available memory was to be dedicated to animation and Music TV-style digitized video, which characterize the interactive scenes of each game. This often meant turning 4 to 10 minute tunes into 2 minute 15 second tunes without damaging their integrity -- that is, each song still had to sound like a whole song and contain the crucial guitar hook.  For example we shortened the Allman Brothers classic Whipping Post from 22:40 to less than 3 minutes!

Next we chose the players for the project and the recording studio in which we would lay down the tracks. Most of the basic tracks were recorded at Tom Waltz's Waltz Audio Production, a 24 track studio in Boston, with a guitar/bass/drum trio (and occasional keyboard). Our biggest concern in choosing the musicians was their familiarity with a wide variety of styles, not only in their playing, but in their sound. This was important given that we had to cover groups such as Lynyrd Skynyrd, The Cult, Steppenwolf, Pantera and Cracker. Drums, male vocals and some guitar work could be covered by Notable.

In order to capture the proper feel of each song, Dan (on drums) listened to the original songs while laying the basics. In this way he could remain true to the spirit of the Songs. Using Yamaha drums, Zildlian cymbals and an arsenal of various snare drums. Recording the drums in a large room aided Dan in getting sounds that were appropriate for each tune.

Our mainstays for guitar and bass were, respectively, Adam Steinberg and Baron Browne, both of whom were outstanding. Adam has gigged and written songs with The Walkers, Patty Griffin, Laurie Sargent, Nicky Holland among others.  He proved useful for deciphering even the most remote guitar parts in a song. His equipment included Fender Twin Reverb and Marshall amplifiers; a DigiTech RP1 pre-amp; Ibanez tube screamer and other effects boxes. Guitars he used included a '67 Telecaster, a '62 reissue Stratocaster, a Gibson Spirit, and a Ibanez Saber.

Bassist Baron Browne has toured and gigged with Jean Luc Ponty, Billy Cobham, and Gary Burton, among others, and has a reputation for being in-the-pocket. We did not need a great deal of variety from him as far as his sound was concerned, and he mainly stayed in the control room, going direct from his 5-string Fender jazz bass running through a Neve 1073 pre-amp and EQ and a UREI 1176 limiter to tape. Other musicians involved in the basic tracks were bassists Lenny Bradford and Matt Gruenberg, guitarists Kevin Barry, Cyril Lance and Stephen Mayone; drummer Jason Fox; and keyboardists Sam Bozeman, Dave Limina and Matt Jenson, all of whom proved versatile and professional.

Our choice for the female vocalist was Sally Sweitzer, who has the voice of a true rocker. As the repertoire of songs for the project became more and more diverse, we wondered if she could fit the bill, but she came through with flying colors. Mark, on male vocals, made his debut in the heavy metal genre with this project, and managed to scream through Pantera, Biohazard, Motley Cre, The Cult and Lynyrd Skynyrd.

The mixing was done at Sound Techniques in Boston, MA. We chose freelance engineer and Berklee Associate Professor, Carl Beatty after listening to some of his work and getting recommendations from some mutual friends. Carl has recorded Keith Richards, Tom Jones, George Benson, Frank Zappa, B-52's -- enough said. Armed with an occasional decaf and ably assisted by Sound Techniques' own David Kirkpatrick, Carl was up for long hours of work. Carl proved to be extremely technically proficient, and patient when our mix criterion changed or was obscure. His sense of humor and session stories kept spirits up when we were bogged down by the unexpected. At one point during a mix the power went out for the entire neighborhood, including Fenway Park, leaving us in the dark for ten minutes and not knowing if we'd lost our automation passes. During the crisis Carl explained that in his mixing classes he intentionally turns off the power to get the students to know how all the machines behave in all conditions. He said "You never know what the client may do, so you might as well the have the security of knowing your machines." True to his professionalism, and thanks to a well timed "Save command" we lost almost none of our work.

[Color photo of mix team]
Daniel C. Cantor, Mark Weltner of Notable Productions, Carl Beatty, freelance engineer, and Dave Kirkpatrick of Sound Techniques, pictured in front of Sound Techniques' SSL 4000G mixing console.

What Carl Beatty brings to a mix session:
A pair of B&W DM100 Speakers
Two Neve 2254 E compressors
One MXR Phaser/ Flanger
His Chair

What Notable Brings to Session:
Two Neve 1073 EQ/Pre-amp
One Drawmer 1960 Compressor/Pre-amps
One Troisi Digital Companion (16-bit A-to-D converter) thanks to Coleman Rogers
One Neumann U87 altered by Claus Heyne

We used an SSL 4000G mixing console, a fully automated board which makes recalling mixes a breeze; each fader and knob position is faithfully memorized, and all mix moves are stored and adjustable. Extensive automation was particularly useful in this project when we needed to  adapt the songs to the needs of the game.

There were several unusual techniques used while mixing. Occasionally, we found that we needed to enhance the bass drum by adding a sampled drum. Using a 16-bit S900 with a trigger unit in tandem with the Russian Dragon (see MIDI issue Jan/Feb '94 for a review of the Russian Dragon), we were able to accurately double the existing bass drum with a sample.

If we played the original kick drum from the playback head to trigger the sampled bass drum, the sample would arrive late, due to MIDI delays and trigger unit's response time.

Figure 1
One of the advantages of analog tape decks is that the tape passes over the record head prior to the play head. This enables you to anticipate the playback of music off the playback head by an amount determined by the tape speed and distance between the heads.

On Time
Early (original kick drum)     Late

Kick drum from
Playback head
into trigger unit/sampler

If we played the original kick drum from the record head to trigger the sampled bass drum (while all other tracks were coming off the playback head), the sample would arrive too soon. This is because the time it takes for the tape to move from the record head to the playback head is longer than the MIDI delays and trigger unit/sampler slowness.

Figure 2

On Time
Early (original kick drum)     Late

Kick drum from
Record head, into
trigger unit/sampler

By using a digital delay after the kick coming off of the record head and before the trigger unit/sampler, we could adjust the arrival time of the triggered sample, making it coincide exactly with the rest of the music on the playback head.

Figure 3

On Time
Early (original kick drum)     Late

Kick drum from
Record head, through delay,
into trigger unit/sampler

We used a Russian Dragon to accurately measure the amount of time that the record head anticipated the playback head on the Sony APR 24-track tape deck. We then used it to measure the delay created by going through a delay (currently set at zero) and a trigger unit/sampler and back to the board. The difference of these two measurements gave us the delay setting needed to have the drum and sampled drum sound simultaneously.

Our original demo version mixes had very little real guitar in the mix to leave a hole for the Virtual Guitar to fill. Reactions to these low-tech versions led us to realize that our client wanted the songs to sound as good as the originals, but at the same time different. One obvious clue separating our versions from the originals was the use of vocalists that were unlike the originals but convincing in their own way. Many of the male vocals were sung by a female vocalist on our versions. This also afforded the video band some sexual diversity.

As a music producer, Notable is accustomed to making sonic decisions based on supporting the song, lyric, mood or sound characteristic we are trying to achieve. For the Virtual Guitar project our mix criteria was most unusual. The first criterion was that the mixes had to preserve the identity of the original song.  Since the song list includes hits from three decades, it required us to be well versed in the mix aesthetics characteristic of each period. The convenience of having the original version on the 24-track in sync with our tracks facilitated switching back and forth between the versions while staying exactly where we were in the song.

The second mix criterion was more ambiguous and actually changed over the course of the project.  The balance between the instrument volumes was partially determined by which virtual guitar part would be played over the top of each mix. In fact, each song would have a number of possible guitar parts played over it. These included most guitar parts found in the original, plus additional parts composed by Mark, Dan and Adam. To make things more complicated, Ahead wanted the mixes to sound full and impressive; the mixes could not sound like a music-minus-one rendition with the assumption that the virtual guitar parts would fill in the missing parts.

The actual sonic characteristics of the Virtual Guitar were in development and not available for us to use during the mix process. Imagine mixing a vocal album without knowing what your lead vocalist sounds like. The attempt to put in real guitars to "ghost" and fill out the mixes while leaving enough room for the Virtual Guitars was unlike any type of mixing we've done. To be safe, we laid as many as ten variations for each mix in order to avoid the possibility of having to remix all 21 songs. This technique saved us a number of remixes and enabled us to stay much closer to deadlines.

To achieve a variety of guitar and drum sounds we often ran the guitar tracks back though amps in the studio and re-mic'd them. Jim Keltner's snare sound on This Is Cracker Soul was particularly open and loose sounding. We created a different sound by using a Radio King 5" x 14" snare during the tracking session, but it wasn't doing the trick. We ended up running the drum track out into the studio's JBL speaker pointing upward. A loosely tuned 7" x 14" wooden Montieri Snare was placed on top of the cone. We then re-mic'd the drum at a small distance, giving us the right mixture of room and drum to achieve a dark, loose quality we had been missing. All of the mixes were double-checked through a two-track Studer A810 mono speaker and recorded into the digital ins of two DAT recorders through a Troisi Digital Companion. The analog to digital converters in this unit are far superior sounding to the front end of most DAT recorders.

Our unedited mixes were then approved and we took them to be mastered at Jonathan Wyner's M-Works in Cambridge, MA. Jonathan, besides being adept with Sonic Solutions, has a great listening environment and an even better set of ears. It's not uncommon for him to discern a number of subtleties of the recording techniques used to make the recording you bring to him. Even more useful is his ability to detect problems and have corrective measures in hand quickly and easily. The music mixes and our cues were loaded into Sonics Solutions via Summit or Aphex, Compression and/or Summit, or Triosi EQ. The endings and beginnings were trimmed and cleaned. All the volume levels were normalized and made comparable.  Drum clicks at the count off that were noisy or inconsistent were replaced with cleaner clicks.

Mixes were then sent to Palomar Pictures in Los Angeles for transferring to video and to Rob Cairns at Big Fish Audio for data translation from 16-bit 44.1k DAT to 8-bit 22k files. Rob has prepared or recorded audio for video games and CD-ROMs, including the Prosonus library. His responsibilities in this project included the translation and assemblage of all audio portions of the game. These included Notable's mixes, loops and guitar riffs, Rob's own sound design, opening score for Lloyd's descent from the heavens and a variety of other cues. Dialogue recorded at Media Recorders in Hollywood was also added at this time.

Once the mixing was finished, it was time to input the MIDI guitar data, ultimately to be played by the Virtual Guitar. The inner workings of the Virtual Guitar are still proprietary at this point but we can say that we created four guitar parts per song. Virtual Musicians (game players) will have the option of mastering these four levels of difficulty, beginning with basic rhythm guitar, advanced rhythm guitar, lead guitar and stunt guitar, which requires extreme musical precision.
In addition, at each stage of their ascent to stardom, players face a series of on-the-spot challenges, such as matching riffs with rivals, sitting in on an after-hours blues session and making rough decisions as unexpected choices are thrown their way.

We used the Roland GR-1/GK-2, which is a combination guitar "pickup" and sound module (guitar not included) to write the guitar parts. The GK-2 MIDI pickup was mounted onto a Stratocaster copy, and we had the action adjusted to optimize its performance. (The GR-1 is one of a number of Roland guitar synthesizer modules that enable the Roland GK-2 pickup to translate its data to MIDI.) By using a MIDI guitar controller, the chord voicings would be correct and the guitar parts could be played on their native instrument, thus reducing translations of techniques to a very different type of controller (e.g., keyboard). Although the Roland GR-1/GK-2 has a reputation for being one of the best and most popular MIDI guitar controllers on the market today, it still had its limitations, as will be described.

We started by syncing the songs to our Macintosh SE/30. This involved recording our audio performances of each song in stereo to a multitrack tape recorder, then striping another track with SMPTE. We then sync'd the songs to Mark of the Unicorn's Performer 4.2 using this SMPTE track via an Opcode Studio 5. As files were created for the songs, a "click track" was created for each. The opening 8 clicks at the top of each song before the music started was triggered into Performer via a trigger to MIDI converter. We then shifted the notes earlier to account for MIDI delays as well the sluggishness of the trigger unit. The click tracks during the songs were subsequently recorded manually (playing along to the song using a DrumKat), and unfortunately did not give us quantization capabilities. At one point we tried creating a "tempo map," in hopes that it would enable us to use quantization, but due to a serial port-dependent bug in this version of Performer, this was not possible. (Note-Mark of the Unicorn has since supplied us with a way around it.)

We used the click tracks to help us when there was a difficult guitar passage to lay down. By slowing down the tempo on the Performer MIDI file and playing along with the click, we could enter information that would have been impossible to track on the Roland GK-2 MIDI guitar at a faster tempo. (By "tracking" we mean the MIDI guitar pickup's ability to identify the notes being played and correctly convert them into MIDI data to be stored on the computer file created for that song.) Of course, we were no longer playing along with the music at this point, since the songs recorded on the tape deck could not be slowed down* to sync with the computer file's new tempo, so our guitarist had to know the tune thoroughly when we used this approach. (* This is true of extreme tempo variations- smaller variations are often still trackable by SMPTE to MIDI converters if you slow down or speed up your deck just slightly.)

We were disappointed with Roland's GK-2 MIDI pickup. It tracked sluggishly and its output was inconsistent. Strumming, a common guitar technique, is a very complex task for the Roland MIDI guitar -- there is a great deal of information to be interpreted and communicated. We experienced large and varied delays in the tracking of the instrument when playing rhythm. In playing lead guitar, we often encountered jagged pitchbend information when playing a note with vibrato, which created more of a trill than a vibrato. Some notes or pitchbend information simply did not make it from the guitar into the computer, regardless of how the guitar was played.

The biggest aid to the tracking delays was to have a competent guitarist who could adapt his technique to the MIDI guitar -- no easy feat. Even after Adam , our guitarist, had reached a plateau on the learning curve for the Roland GK-2, we spent many weeks painstaking playing and replaying songs to simply compensate for poor tracking. Furthermore, new playing techniques were constantly explored for different material, and there was no consistent method. Occasionally a passage would call for finger picking the strings lightly; on other occasions, they needed to be hit hard with a pick.

One method used to correct delays was to edit shift the position of the notes in the Performer so that they occurred in the proper place. One might ask why we couldn't simply shift all information backwards by a given amount in relation to the music. However, after trying this, it soon became apparent that the delays were inconsistent, and events had to be treated individually.

Tracking problems of the MIDI guitar were also string-related, the 6th and 5th strings (the low pitches) being the worst culprits. When one of these strings was struck repeatedly the problems increased exponentially. A perfect example is the opening riff of Whipping Post, a fast repeated pattern that is played primarily on the 6th string, and on the 5th as well. Adjusting the sensitivities of these strings on the GK-1 did not help. We overcame the problem by playing the riff an octave up on the 3rd and 4th strings, then transposing it and moving it over to the 5th and 6th strings. Songs that had guitar parts featuring de-tunings (a common sound and technique for these styles of rock) had to be played higher up and transposed as well.

Another problem was the spontaneous generation of notes from a sustained chord. These generally occurred as harmonics of the chord being held. We would suddenly hear a note jump up by an octave or two -- taking it off of the fretboard! In this case, we would either re-record that chord, or edit out the extra note and extend the duration of the note that had been cut off to match the other note durations of the chord. We also found the mysterious appearance of note-on information followed immediately by a large pitchbend. The note-on would be a wrong note, and the pitchbend would compensate, bringing it instantly to the correct note. As you can imagine, trying to edit individual notes that appeared in this way was frustrating and time consuming.

We also encountered large numbers of redundant note-on information with tiny durations. For example, a note of 15 ticks duration might be immediately followed by the same note with the correct duration. Sometimes these were barely audible, other times they severely clouded the performance.

The unifying factor and ugly truth in all of these problems is that all of them occurred when the Roland MIDI guitar was being played "correctly." This is not taking into account the usual extraneous note-on information resulting from strings being struck inadvertently from string stretches, extra pick hits, etc. -- events that we take for granted in an analog guitar performance, but that needed to be deleted in this unique situation.

Fortunately, Virtual Guitarists don't face the trials we faced with the Roland MIDI guitar. Still, it has its challenges -- meet "Chops" Felton.

One of the characters who populate the fictitious town of West Feedback is ace guitarist "Chops" Felton, who challenges you to a guitar duel. He throws his best licks at you, your goal is to match him note for note in order to move to the next level -- in front of a unusually perceptive audience.

For this part of the game we hired ace guitarist John Mason to come in and play a variety of rock guitar styles paying homage to Clapton, Vaughn, Hendrix, Page, Beck and Van Halen, to name a few.  John (as Chops) heard a one measure click and then played a two-measure lick. Following Chop's lick the click appears again, signaling the players chance to imitate Chops. For John's part of the recording we used a Marshall Jubilee half-stack, Chandler tube driver and Johns trusty 1972 gold-top Gibson Les Paul.

When it arrives this fall, the Virtual Guitar will have challenged its creators as well as those who dare to play the game. We have only begun to describe the plot twists that unfold within this game. The characters and script exude humor and a rockin' intensity that you're not going to forget. If you practice you might just have "what it takes" to reach the top: jamming with a great band in front of a pumping audience. With Lloyd at your side and your ax strapped across your chest you can slip into the world of rock'n'roll.

Dan and Mark would like to thank Michael Goldfinger and Aimee Good for editing work. Notable Productions is a  music composition and production company located Watertown, MA, and has recently scored the theme music for a movie on fatherhood for Vice President Al Gore. Notable has not informed his wife, Tipper, of our rock'n'roll tendencies.

updated: 11 years ago