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Tonal Plexus FAQ

Q: Hey, is that thing made of legos?

No. There are no legos used in the construction of a Tonal Plexus. I didn't realize how much it looks like legos until everybody started saying that. I agree, it does look like legos. This was not done consciously. I have no affiliation with Lego and I am not using the Lego™ trademark with any kind of permission. I have a lot of respect for legos; they're great.

Do you have any plans to support Open Sound Control in the U-Plex?

No. U-PLEX is a native USB-MIDI device, but if you need OSC you can use it with applications that receive MIDI and convert it to OSC, such as MAX.

Q: What sort of key action does the Tonal Plexus have?

The keyboards use high-quality low-noise positive-clicking tactile-contact key-switches having a light touch (60 grams of force), a key travel of about 0.3 mm, and a longevity rating of 5 million cycles. Some advantages of this system are minimal fatigue and easy, natural achievement of effects such as glissandi, narrow clusters and chorusing.

Q: What do the key surfaces feel like?

The keytops are made of high quality hard plastics formed with beveled edges and arrayed in a consistent pattern of three diameters, the largest of which is concave.

Q: I'm a pianist. Can you describe how the Tonal Plexus feels different from a piano?

In comparison with a piano, or a traditional piano-style keyboard, the Tonal Plexus keys are not lever action, and they are also not large solid-feeling objects. Instead, the keys are all small buttons which respond to a light touch, and also are free to be guided by touch very slightly in all directions. This involves a technique which is quite different from piano playing, although it may be said to be somewhat related to pipe organ and harpsichord technique. Of all traditional keyboards, the Tonal Plexus keyboard may feel closest to the clavichord, in that the connection with the keys has a feeling that is very much in the fingers and the keys can move ever so slighltly, which allows for a delicate playing style. I have found that most pianists initially have a negative reaction to the Tonal Plexus keyboard, because although the piano arrangement is easily found in the key layout, the keys themselves don't feel like piano keys at all. Pianists have initially described the keys as feeling "toy-like" and "fragile". After a brief period, however, a pianist will usually end up liking the action once he or she gets used to it, realizes its potential and sees it as the right thing for acheiving musical results which are simply impossible using a traditional piano style keyboard having much larger heavier keys.

Q: Can I use the Tonal Plexus to retune my [VST/RTAS/AU] software instruments?

Yes, if the software instrument supports pitch bend. It is best if the software instrument is also multitimbral, such as the USM synthesizer in Cubase LE, in which case you can use one instance of the instrument to get retuned polyphonic output. But if the instrument is not multitimbral (the more common situation), then several instances of the instruments must be created in order to have polyphonic output. This is the main reason that channel switches are provided on the TPX, so that the software instruments you create can be linked directly to the TPX sending channels. For example, if you plan to play up to 6 voice chords, then you need to create 6 instances of the software instrument, each receiving on a different MIDI channel, and then engage only those MIDI channels on TPX. Most programs allow you to create one software instrument and copy it to make more instances of it. In some programs, such as the EXS24 instruments in Apple's Logic, the pitch bend range of the instrument must be set to 1. After doing this, the instrument can simply be copied and the only additional step necessary is setting the receiving MIDI channel to be different on each instrument, and making sure that those channels are the same as those selected on TPX. In Logic, you need to also select 'demix input by channel' and on Digital Performer and other programs you need to select 'multi record' to record multiple MIDI tracks at once, with correct channel assignments. Once you get the hang of it, the process is relatively painless. See also the information on setting the pitch bend range for MIDI tracks on the general FAQ page.

Q: What is difference between the TPX4 and the TPX4s?

The TPX4 (or any other TPX keyboard lacking an 's') is only a controller, which outputs MIDI to control an external synth, so it requires a MIDI cable and another unit, power supply and amplifier. The TPX4s (and any TPX model with the 's') has a GM synthesizer and amplifier already in it, so it's totally self-contained. The latter is more useful when you want to move the keyboard around and be able to set up and play easily. Although the built-in synthesizer is only a basic GM soundset, another advantage of the 's' models is that the amplifier has audio input, so an external sound module can be used without having to haul around an external amplifier. The internal amplifier is a powerful 22 Watt unit with a big sound that can be equalized using switches on the keyboard.

Q: What kinds of sounds are in the internal synthesizer?

The internal synthesizer is a simple unit which has the basic General MIDI soundset, plus a second bank of alternate sounds which are variations on the same sound set. It is a sample-based synth, which in its basic form is comparable in quality to the GM sounds of the Windows or Mac OS software synths. The main advantage of having this internal synth is that it tremendously simplifies use of the keyboard, allowing the keyboard to make music simply by powering up, using only a single power cord and no external MIDI cables, MIDI modules or amplifiers. This is a considerable advantage since external MIDI gear can require its own setup steps, including power-up sequences and configuration, and lugging around more equipment including heavy amplifiers makes the whole process of using the keyboard more work. Additionally, having an internal synthesizer allows the physical controls of the synth to be used to tweak the sounds in special ways. TPX2s and 4s have controls for shaping the waveform envelope attack, decay, and release, as well as controls for EQ low, middle and high frequencies. Using these controls, the internal sounds become quite flexible and can be tweaked to render a wide variety of results. The 6s and 8s keyboards have additional controls for changing other internal synth parameters, including effects and filters. Further documentation of the synthesizer can be found in the TPX6s/8s User Manual (PDF). Since September 2008, the PXSC Plexus Synth Control application can be used to tweak the sounds on all TPX keyboards having the synthesizer option.

Q: What kinds of volume pedals can I use with the Tonal Plexus?

The keyboards have volume pedal inputs for controlling MIDI key velocity and MIDI volume. The sliding faders on the keyboard itself are 20KOhm, and the pedal should also be 20KOhm. Guitar volume pedals which are high impedance will not work very well. In the US, currently I am recommending the Apex AFP3. With this pedal, you will need to get a cable which is 1/4'' Stereo plug to 2 1/4'' Mono plugs (a.k.a a standard Send / Return Insert Cable), such as STP-200 from Hosa. In Europe and the UK, I recommend a pedal made in Italy by bespeco, the VM16L. This pedal is nice because it has the cable built in. A pedal basically the same as the Apex AFP3 is also available in Europe from bespeco as the VM14L. Customers in Australia can use the Proel PVP16L, which is basically the same as the bespeco VM16L.

Q: Is every key on the keyboard retunable?

Yes. To get a feel for the flexibility of the keyboard tuning, please try out the free software TPXE Tonal Plexus Editor.

Q: Will the Tonal Plexus retune software instruments like Garritan Orchestra?

Yes. Depending on how you are working with the samples, you can use either the tuned output from the keyboard (OUT) which requires an instrument per voice (channel) of the selected polyphony, or you can use the untuned output (THRU) to send raw MIDI note messages if your sample playback software already has its own microtonal key mapping support. Garritan is a good choice for microtuning because it supports scala .scl files, so you can play microtunings with increased polyphony, but going that route requires you to set up tuning tables in Garritan, which has limitations and does not allow changing tunings on the fly, which is nowhere near as flexibile as using the tuned output from TPX.

Q: Why doesn't the Tonal Plexus have velocity sensing keys?

Velocity sensing keys would be nice, but on an instrument like the Tonal Plexus, they become impractical in terms of design constraints and cost. Although velocity sensing can be achieved in may ways, the most common way is to use lever action keys with two switches per key. On a 12-tone keyboard, this is not such a big deal, but right away you can see that an instrument that has 211 keys per octave immediately becomes an instrument with 422 switches per octave. That means a four octave keyboard now has 1688 switches, and an eight octave has 3376 switches. And supplying a lever key action for the Tonal Plexus layout is rather involved (see the 2003 prototype which uses an early abandoned layout). It was determined that lever action keys were not suitable for the final layout.

The small size of the keys prohibits normal dual switch designs (two switches at different heights, or different locations on a lever). Single actuator dual action pushbuttons normally require compression springs, which give the wrong tactile feeling for a musical instrument (resisting more as the key travels down). There are other types of dual action switches, but these typically cost about twenty times (!) as much as the switches currently used on the Tonal Plexus.

There are additional costs to be paid in terms of the electronics. Velocity sensing is normally achieved by subtracting the clock values of two contacts for each key, so in addition to doubling the switch count, an increase in the overall keyboard scan rate is required. The scan rate cannot exceed a few milliseconds before velocity sensing is noticeably unresponsive. In the case of a Tonal Plexus keyboard, the increased speed needed is quite considerable, since we are now talking about thousands of contacts to scan with millisecond precision.

While the physical constraints are obvious, it can also easily be seen that having twice as many keys with faster electronics more than doubles the overall cost.

There are other methods which could be used to achieve velocity sensitivity, such as the addition of a limited number of piezoelectric elements or other sensors per octave. This may lead to something in the future, but so far experiments along these lines have not been satisfactory.

But the good news is, there are ways to control the velocity which result in very natural sounding output from the Tonal Plexus. A fader allows the velocity to be controlled while playing with one hand. A volume-style foot pedal can be used to control the velocity while playing with both hands. To avoid the mechanical sounding effect of a constant MIDI velocity, there are also two DIP switches which allow selection of a velocity randomization bandwidth. The available ranges are 10, 20, or 30 MIDI values. The state of the fader or pedal becomes the center value of this randomized bandwidth. Using either of these options, apart or together, creates natural sounding output with degrees of control that make sense given the prohibitive design problems and overall expense of standard methods of velocity control.

When thinking about this issue of velocity sensitivity, it should finally be noted that the Tonal Plexus provides its unique musical expressiveness directly through its discreet control of pitch, and that fact alone makes it much more musically expressive than a standard keyboard.

Q: Why don't TPX keyboards have a USB port?

TPX keyboards are stand-alone peer-to-peer MIDI instruments. U-Plex keyboards are USB computer peripheral instruments. Please visit the General FAQ page for details.

Q: How does the Tonal Plexus compare to the [Cortex Design Terpstra] [C-Thru Music Axis-64] [Haken Audio Continuum] [Starr Labs Uath-648, Uath-880] [Thumtronics Thummer]?

Please visit the Comparison Charts page.

Q: Why have I not seen a review of a Tonal Plexus in a major music gear magazine?

To date I have been contacted by only one potential reviewer from a major music gear magazine, and they asked me to send them a keyboard for free. It is not possible for me to send away free keyboards.

Q: Why have I not seen ads for Tonal Plexus keyboards in music gear magazines?

At present I simply cannot justify such expenses. If you look for my advertising budget, you will see only a bill for internet hosting. You won't even find hours logged for YouTube videos, because videos are simply made in 'spare time'. I hope that you will support me for choosing to keep my costs as low as possible so that my products can be affordable. Not publishing expensive ads is one way I am keeping prices low when every product is being made one at a time by hand. This situation may change in the future, when my products are being mass produced.

Q: Do you offer educational discounts?

No, but if you want to arrange an order for more than one unit, I may be able to offer you a quantity discount.

Q: I am with [ _ magazine] [ _ music group] [ _ College] [ _ University]. Can you send us a free keyboard?

No. You are welcome to buy the keyboards.

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