While MIDI sequencers make an excellent job of allowing you to create a fully orchestrated backing track, unless you go to the expense of adding hard disk recording facilities or buying a sampler with a huge amount of memory, you can't use a sequencer to record vocals or 'real' instruments. While I'd be the first to accept that in the context of pop music, MIDI instruments are often just as useful as the real thing, even the most skilful synth player will find it difficult to emulate the virtuoso performance of a solo guitarist or sax player.
So when it comes to capturing a 'real', as opposed to virtual performance, tape is still first past the post for cost effectiveness. Both multitrack tape and MIDI sequencers have their strengths and weaknesses, so rather than playing one off against the other, it's far more useful to make them work together. You could just mix your MIDI sequence, in stereo, to two tracks of your Portastudio and then overdub your vocals or solos on the remaining two tracks, but that isn't the most effective way to work. There are far greater advantages in making the tape machine and sequencer run side by side, in sync, so that the MIDI instruments never have to be recorded onto multitrack -- and you only need a little relatively inexpensive hardware to do this. What are the advantages? Probably the most significant benefit is that, because you don't actually record the MIDI instruments to tape at all until the final mix, you can change the balance of the instruments, select different patches and set up different effects, right until the last minute. You'll also find that the end result is cleaner because you're avoiding one generation of tape. Adding a 16-track sequencer to a 4-track cassette multitrack effectively gives you a 19-track recording system (you lose one tape track to time code).
If there's a disadvantage, it's that you'll need a mixer with enough inputs to handle both your taped sounds and your MIDI sounds, and if you have several MIDI modules, you might find that the mixer stage of your cassette multitracker doesn't have enough inputs for the job. If you're using an open-reel machine, you don't have the same limitation, but you still need a mixer with enough channels.
While it's technically quite easy to control the playback speed of a MIDI sequencer, it isn't quite so easy to control a typical semi-pro multitrack recorder, so the most practical option is to make the sequencer run in sync with the tape machine rather than vice versa. In other words, the tape machine sets the pace and the sequencer follows. This involves getting the sequencer to start at exactly the right time relative to the tape machine and, once it's running, to keep it in time until the tape is stopped.
So far, I've described what working in sync has to offer, but how does it work in practice? How is the sequencer able to start at the right time and keep in time with the tape machine? The answer is time code -- a series of electronic markers or signposts that are recorded onto one track of your multitrack. You can think of time code as being the electronic equivalent of the sprocket holes that guide cine films through projectors, and though you lose one track of tape to hold the time code, you can use it to sync up as many 'virtual' MIDI tracks as your sequencers and sound modules can provide.
The simplest form of sync is known as FSK (Frequency Shift Keying), a system which records a series of electronic tones (usually 1kHz and 2kHz bursts) onto tape, at a tempo related to the tempo of the song you're working on. These tones are derived from MIDI clock, which is based on sub-divisions of the song's tempo. Many drum machines have FSK sync built in, which means that even if you don't have a sequencer, you can still sync your drum machine to tape.
Once you've sorted out your song arrangement, the starting tempo, and any subsequent tempo changes, it's simply a matter of playing back your programmed song and recording the code to tape. Because the code is tempo related, if the song speeds up, the code speeds up, so there are no conversion processes or other complexities to worry about.
Once the code is safely on tape, the output of the code track is fed back into the sync input of the drum machine (or whatever MIDI device you're using), the drum machine is set to external MIDI sync, and you're in business. Providing you start the tape before the start of the song, the drum machine will receive a MIDI start command and run in perfect sync with the tape.
Here's the procedure for working with a drum machine or sequencer equipped with FSK:
Program the complete drum machine part or, if you're using a sequencer, the rhythm part of your sequence, including any tempo changes.
Record the sync code output from the drum machine (or sequencer) onto one tape track, (usually the highest-numbered track), while allowing the drum machine to play the piece you have just programmed. The drum machine is set to internal sync during this process.
Note: Some tape machines have dedicated sync ins and outs, while with others, you have to use the audio ins and outs. In the latter case, bypass any noise reduction and EQ, if possible, as leaving them switched in may make the code read unreliably.
After the code has been recorded, plug the output from the sync track into the Sync In socket on the drum machine. Switch the drum machine to Tape Sync, and play the tape from just before the start of the time code.
The drum machine will start when it receives the sync code from the tape machine and will stay in time with the tape until you stop the tape machine.
After checking that the code is being read reliably, you can now go on to record your tape tracks while monitoring the sequenced parts.
Important: make sure you don't accidentally erase the sync code, otherwise you won't be able to get the song sync'ed up again.
The main disadvantage of simple FSK is that whenever you stop the tape, you have to wind back to the start again to restore sync, which can be a real pain when you're working on the end of a long song.
Other MIDI equipment with external MIDI sync capability can be sync'ed to the drum machine via MIDI, which means that you could use your drum machine to sync a MIDI sequencer to tape. Figure 1 shows a practical way to do this. Note that when working with FSK, you can't record new parts onto the sequencer while you are sync'ed up because the sequencer's MIDI In is occupied by the drum machine's MIDI Out. If you must work on your MIDI parts while listening to the tape parts you've recorded, you'll need to buy a MIDI merge box to combine the MIDI Out of your master keyboard with the MIDI Out of the drum machine. Figure 1b shows how this works.
The basic FSK system works fine, but its weak point is its inability to establish sync unless the song is started from the beginning every time. An enhanced version of FSK, known as Smart FSK, gets around this very neatly, providing that the sequencer or drum machine being locked up recognises MIDI Song Position Pointers (as most modern units do). Smart FSK may be used in exactly the same way as basic FSK, the difference being that you can start the tape anywhere in the song and you'll be sync'ed and running within a second or two.
Smart FSK is used by some external sync boxes, and even if your system has basic FSK sync, it may well be worth buying a Smart FSK box just for the luxury of being able to start your song anywhere you like. Some of the available Smart FSK units (such as the JL Cooper PPS II) include a MIDI merge facility so that new sequencer parts can be recorded while you're running in sync. Figure 2 shows a system using such a Smart FSK box. In this example, the drum machine is running as a slave from the sequencer's MIDI Out, but providing your drum machine recognises Song Position Pointers (SPPs), you could equally well sync the sequencer to the drum machine. If you're not working to picture, Smart FSK will give you all the practical benefits of SMPTE but with fewer complications.
SMPTE (pronounced simp-tee), is a highly sophisticated time code developed originally for soundtrack work in the film and TV industries. Unlike the previously-mentioned FSK systems, which rely on the tempo-related nature of MIDI clock, SMPTE places a stream of electronic markers on tape, each marker containing coded timing information relating to elapsed hours, minutes, seconds and frames of film or TV picture. The code is quite independent of musical tempo, and there are several versions of SMPTE in use to accommodate the different frame rates of film, PAL TV or NTSC TV. Though it was developed for soundtrack sync'ing, SMPTE may also be used for non-picture related applications, and now that all the hardware is available on a single chip, it has become practical to use this time code for general audio sync. SMPTE has been used for a number of years for sync'ing two multitrack tape recorders, but its affordability in recent years now makes it a viable option for use in MIDI studios.
Because SMPTE isn't related to tempo, a whole tape can be recorded, or 'striped', with code before any recording or programming starts. However, as SMPTE measures time, not tempo, a conversion is necessary to translate a SMPTE location to a bars and beats location if it is to be musically useful. This may be done by the computer used to run the sequencing software, or by a microprocessor inside a stand-alone SMPTE-to-MIDI sync box. To do this conversion, the system needs to be given the start tempo of a piece of music, the precise time at which the sequencer is to start, and information about the locations and values of any subsequent tempo changes. This data must be stored as a 'tempo map', and this tempo map must be loaded each time the song is worked on. A general-purpose SMPTE-to-MIDI box will normally expect the user to furnish the information needed to build a tempo map, but some of the leading sequencer manufacturers offer dedicated SMPTE sync units which handle the creation and storing of tempo maps for you via the sequencing software.
If SMPTE offers no practical advantages over Smart FSK and also requires you to deal with tempo maps, why bother with it? A good question. I'd say that unless your sequencer has a piece of related hardware, such as E-Magic's Unitor, which makes the procedure transparent, or unless you need to work to picture, you don't need to bother -- stick with Smart FSK. If SMPTE has a practical advantage for music-only use, it is only that it allows you to stripe the tape at any time rather than having to wait until the song is programmed. The only time you're really forced into using SMPTE (see also MTC) is if you're doing work that has to be sync'ed to TV or film.
A comparatively recent offshoot of SMPTE, designed specifically for use with MIDI equipment, is MIDI Time Code, or MTC. As far as the user is concerned, MTC behaves much like normal SMPTE except that it can be piped along a MIDI cable and read by any MTC-compatible sequencer or drum machine. You still need an electronic box to interface the MTC signal with tape, but because the code is handled in the computer rather than by the external box, the sequencing software can look after all the tempo mapping for you. Because MTC is a standard, there should be no restrictions on which MTC sync box you use with your sequencer, and virtually all current MIDI sequencing software is MTC compatible. Even when working to picture, it is now common practice to use a sync box that converts SMPTE to MTC. For example, for Mac users, MOTU's MIDI Express reads and writes SMPTE, generates MTC, functions as a multi-port MIDI interface, and still finds enough time to double as a MIDI routing system. Opcode's Studio series of MIDI interfaces also perform similar tasks. MTC now seems to be the standard sync system supported by the majority of hardware and software manufacturers, so if your equipment supports it, the message is that you may as well use it.
Basic FSK will get you up and running, locked to tape for little expense -- or none at all if your drum machine or sequencer has a sync function built in. On the whole it's easy to use and reliable, providing you bypass any noise reduction systems, especially dbx, and follow the manufacturer's instructions regarding the best level of time code to put onto tape. However, it does have the one major weakness that you have to start your song from the start in order to achieve sync. Once you stop your tape, you have to wind back to the start.
Smart FSK is a great improvement, because you can start the tape anywhere you like and the sequencer or drum machine will still come in right on cue. With any time code system, smart or otherwise, that ties up the MIDI in socket on your sequencer, you'll need a MIDI merge box if you want to record new MIDI parts while still sync'ed to tape. However, some sync boxes have MIDI merge built-in, so check this when you're shopping around for one. You may have to pay a little more for a unit with built-in MIDI merge, but the chances are it'll still be cheaper than buying a separate merge box.
Technically speaking, SMPTE is a sledgehammer to crack a nut, but if your hardware takes care of all the tedious stuff like tempo maps, there's no reason not to use it. On the other hand, if you're working to picture, you'll have to get involved with SMPTE or MTC.
MTC has become the musical sync standard in recent years, but you still need to use a sequencer that can deal with tempo maps. Fortunately, all the current major sequencing software packages do. For example, sequencers such as Cubase or Logic work out their own tempo maps based on the current song data and store the tempo map information as part of your song, so you don't even have to think about the process once you've set a start time. Such systems are almost as simple to use as Smart FSK, though when using either SMPTE or MTC, you should take care to ensure that the song starts well after time zero, the so-called midnight hour. A great many SMPTE systems get very confused if you play through time zero (00:00:00:00) so it's best to put in an offset of between 10 minutes and one hour.
When you run a sequencer in sync, you don't need to put the MIDI sounds onto multitrack at all, though many people still do, either for added security or because they don't have the polyphony do play the whole arrangement in one pass. Avoiding going to tape, especially with bright or percussive sounds, avoids a generation of quality loss, which can be significant if you're using a cassette multitrack. Mastering to DAT can give near CD-quality results, even when your vocals and lead guitar have been recorded on a budget multitracker.
It's obviously a problem trying to use sync code with a multitracker if you only have access to the stereo output. Whatever else happens, you don't want the code to become part of the final mix, so look at the block diagram in your multitracker manual and see if there's any way to get the signal off a single tape track, to the outside world, avoiding the stereo mix. If you have four direct outputs, there should be no problem, but even if you haven't, it may be possible to route the sync track to the outside world using one pre-fade (sometimes called Foldback) aux send and then turning the channel fader right down.
As a last resort, you could pan all the on-tape sounds left and the sync code right. This means that all your off-tape sounds will be mono, but in the context of a stereo MIDI mix, this might not matter too much. After all, vocals and instrumental solos are usually expected to come from centre stage.
The initials SMPTE stand for 'Society of Motion Pictures and Television Engineers' and describe an industry-standard time code designed for use in the film and TV industries. SMPTE code relates to the American TV format of 30 frames per second (fps) and film at 24fps. European TV runs at 25fps and is correctly referred to as EBU. A code combining both formats is properly entitled SMPTE/EBU, but the EBU part is often dropped and SMPTE used as a cover-all term. In addition to the more common 24, 25 and 30fps TV/film formats, the SMPTE standard also includes 'drop frame', which is used only when converting film to TV. The term 'drop frame' comes about because whole frames of picture are periodically discarded, or dropped, to eliminate cumulative timing errors which would cause the sync to drift noticeably over the length of a film.
Drop frame is not used in audio-only applications, and it is normal to set the SMPTE (or MTC) format to the local TV standard (25fps in Europe, 30fps in the USA).
Tape noise reduction can affect the reliability of time codes, so it's best to switch off the noise reduction on your sync track if at all possible. If the multitrack has a dedicated sync input and output, these probably bypass the noise reduction and EQ, but you may need to experiment with the code level to get it to play back reliably. Record at too low a level and you may misread the code, causing the timing to drift, but if you record at too high a level, you may hear the code 'bleeding' into adjacent tracks.
Noise reduction systems from dbx seem to cause the greatest reliability problems, while Dolby C doesn't seem to affect code reliability nearly so much. Some of the very early multitrackers only allow the noise reduction to be switched on or off globally, which means either recording the code with noise reduction or putting up with a lot of tape hiss. If you decide to leave the noise reduction on, you have two options: sometimes it can be best to record the code with no noise reduction, switching the noise reduction back on after the code is safely down. Alternatively, you can leave the noise reduction in all the time but experiment with both level and EQ until you find a setting that works reliably.