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Yamaha Portasound MK100

Programmable Personal Keyboard

A personal keyboard that lets the musician think for himself, from the people who make more of them than anybody else. But is it really more than just a toy? Vince S. Hill thinks he knows the answer.

First shown at the Frankfurt Music Fair earlier this year, the MK100 represents Yamaha's first attempt at giving the much-maligned personal keyboard some degree of user-programmability. Vince S. Hill managed to get his hands on the first example to hit the UK.

The MK100 is instantly recognisable as being a rather different animal to most other members of the personal keyboard species by the fact that, above a panel containing the more commonly found function controls, it features a second control panel labelled the Multi Menu, and it's here that the instrument's user-programmable functions are to be found.

First things first, though.

The MK100 has a miniature seven-note polyphonic, four-octave keyboard (C-to-C) and in common with several competing models, can be powered in one of three ways: using internal batteries, an optional AC power adapter (PA1) or a second adaptor (CA1) that fits into a car cigar lighter socket. Output is stereo, and two integral amplifiers feed two watts per channel into the eight-ohm, 9cm diameter speakers situated at either end of the keyboard's control panel.

Concentrating first on the lower - more conventional - panel of controls, these are from right to left, the power on/off switch (complete with LED indicator), the voice selectors (labelled 'Orchestra'), the rhythm machine controls, auto bass chord section, and master volume control.

There are 12 preset tones, selectable using six pushbuttons and a bank switch that incorporates two LEDs to indicate which bank of voices has been chosen. The sounds are Organ, Trumpet, Saxophone, Piano, Harpsichord, Synthe (I & II), Guitar, Music Box, Oboe, Violin, and Piccolo. This selection represents a nice mix between percussive and chordal textures (though the Multi Menu can be used to alter tone and envelope, more on this anon), and all preset voices can be 'improved' by the use of the 'Stereo Symphonic' pseudo-chorus unit. This has three modes. In the Off position, no effect is produced and the MK100's output remains in mono, the Chorus position provides a slow, phasing modulation, while switching to Tremelo gives a more rapid modulation somewhat reminiscent of that produced by a rotary speaker. Perhaps not surprisingly, this last variant is at its most effective when used in conjunction with the Yamaha's organ presets.

There is also a dual-mode sustain option, this being capable of simulating both a long, concert hall-type sustain (Mode 1), or a shorter effect more akin to that produced by the sustain pedal on a piano (Mode 2). In general terms, voices such as Violin, Music Box, and the Synthe tones worked best in the former mode, while more percussive sounds (eg. piano and harpsichord) were at their most effective with the latter.

Rhythm Unit

As with the preset voices, there are 12 pre-programmed rhythm patterns from which to select, and this is done by using the same bank system described above. The preset rhythms are as follows: Disco, Rock and Roll, 8-Beat, Rhumba, Swing, March, 16-Beat, Shuffle, Bossa Nova, Samba, Slow Rock and Waltz. Two sliders are used to determine rhythm unit volume and tempo, the latter also setting the rate for the Auto Bass Chord section. Seven percussion sounds make up these rhythms, and these are of quite passable quality considering the MK100's price category. Pre-programmed fill-ins are also available, these being activated by use of the Fill-in bar-tapping this once gives one fill in isolation, while holding it down results in the roll sounding continuously.

The Auto Bass Chord section has four slider levers, a volume control, and a three-way switch for Normal Keyboard (ie. off), Single Fingered Chord, and Fingered Chord modes. The section operates over the lower 19 notes on the MK100's keyboard, and although in most respects the system's operation is pretty conventional, one point worth mentioning is that unlike many such systems, the auto-accompaniment switches itself off when a fill-in is selected, which certainly makes the backing more effective.

The Melody Plus feature works in conjunction with the Auto Bass Chord section, and supplies either one or two harmonising notes to each note of an auto-chord, depending on whether it's switched to Duet or Trio.

Multi Menu

Thus far, the Yamaha has been little more than a run-of-the-mill personal keyboard with a couple of clever 'sound enhancement' features and a conspicuously low price tag. However, it's the Multi Menu section above the main control panel that really sets the MK100 apart from the crowd. Broadly speaking, this section is made up of nine different functions (or 'menus'), and I think it's worth examining each of these in turn.

Waveform Synthesiser

This option also goes by the name of Melody Voice Vari 1, and enables the user to alter the waveshapes of any of the MK100's factory preset voices using eleven different shaping alternatives. To change a sound, all you do is select the Orchestra voice required, and select two waveforms from those displayed by the menu. Since each preset sound is only made up of two waveforms in the first place, the menu enables you to change a preset voice beyond all recognition, particularly if you add vibrato (switch 12) when there was none to begin with, or vice versa. As an example of how the system works, I managed to turn Yamaha's trumpet approximation into quite a plausible clarinet, simply by changing the waveforms to 4 + 11 and removing the vibrato. Once you've got a sound you're happy with you can store it in a memory bank, labelled 'Custom' to distinguish it from Yamaha's own group of voices (labelled 'Preset'). Your own tone colours then remain stored in memory even if you subsequently select another menu or even turn the power off.

Envelope Synthesiser

It will come as no surprise to most of you that this menu also goes by the name of Melody Voice Vari 2, and that this section operates in a similar manner to Vari 1 except that in this case the subject for user-variation is the envelope of a sound. The menu works in an almost identical way to the waveform synthesiser, except that in this case there are only ten variations available, switches 3 and 12 being inoperative. The MK100's menu display lists the variable parameters as attack, decay and sustain, but in fact this last is more accurately described as release time in traditional synth terminology. Each of the ten operating pushbuttons refers to a distinct (non-programmable) envelope pattern, these being graphically illustrated on the above-mentioned display, so user confusion is unlikely.

Incidentally, combining the sound-adjustment possibilities presented by Melody Voice Vari 1 and Vari 2 results in a total of no fewer than 1376 tone colours being available - quite a remarkable figure, even if only a small number of those permutations is particularly musical.

Melody Mixer

A relatively simple menu, this one enables you to play two instrument tones combined in unison, regardless of whether they are Preset or Custom voices. The menu display details all the Custom sounds you've stored in the MK100's memory, and all you do is select one Orchestra preset to go with your chosen user-programmed voice. It should be noted however that the Trio function within the MK's Melody Plus section will not work once you've mixed two sounds together, though quite why this should be the case isn't particularly clear...

Chord Voice Vari

This menu allows you to program a selection of different sounds to take the parts presented to them by the built-in Auto Bass Chord feature discussed above. Once you've selected which preset voice you'd like assigned to the ABC (and again, this can be either a Custom or a Preset sound), that voice remains in this particular menu's memory, even if you subsequently change the sounds using either or both of the Melody Voice Vari menus.

Bass Voice Vari

In its normal (ie. not messed about by the machinations of the Multi Menu section) mode of operation, the MK100 automatically assigns the Guitar factory preset to the built-in bass line function, but as with the ABC menu above, this one allows that arrangement to be altered by the user, so that either Preset or Custom sounds can be used to play the bass line in sync with the drum machine and auto bass chord accompaniment.

Although this might not sound a particularly notable facility, in practice it's quite useful since the bass line subtly alters the envelope of whichever voice you've selected to play it, so that, for instance, the Music Box factory preset becomes transformed into a series of pretty realistic steel drums. All rather clever stuff, really.

Custom Drummer

This menu, perhaps not surprisingly, allows you to create your own drum patterns in memory and store them. Small graphic representations of each of the available percussion sounds (bass drum, snare, open and closed hi-hat, banjo (!) and conga) manifest themselves above six of the Multi Menu section pushbuttons, while a further three of these take on the functions of Preset, Custom Program, and Cancel, switches 3 and 5 being inoperative in this case.

Slightly confusingly - though quite logically - rhythm patterns are created in much the same way as custom instrumental voices, ie. you select a preset rhythm that's fairly close to the one you're looking for and then cancel or insert the various percussion voices until you've got what you're after. The selected preset rhythm pattern repeats in a two-bar pattern to make custom editing a little easier than the above description might make it appear. Pressing Rhythm Stop automatically stores your 'customised' rhythm in memory, and a maximum of 12 such patterns is recallable, though unfortunately you can only modify the preset patterns once each, which can make editing some of the less usable factory presets a rather laborious process.

Custom Bassist

No prizes for guessing that this menu enables you to load your own bass lines into the Multi Menu's memory in place of Nippon Gakki's pre-programmed riff. You can program - using four of the 12 pushswitches, labelled Preset, Custom, Program, and Cancel - one bass line per rhythm, or 12 in all. However, these can be either Preset or Custom patterns, and the menu will also memorise which bass sound you choose to play your custom riff with. All in all, a pretty powerful menu...

Music Programmer

This menu has three basic functions. It allows you to store either chord progressions or melodies, and also allows you to edit the auto bass feature.

Controls on the Music Programmer are as follows: Start/No Chord, Melody/Manual Bass (off-record-playback), Melody, Manual Bass, Chord (off-record-playback) and Auto Bass Edit.

Storing chord progressions (maximum space in memory 250 chords or bars, whichever comes first), is accomplished in real time. All you do is select Chord record (switch 10) upon which a metronome LED begins flashing and you can start playing. The menu will store all information concerning arrangements of preset voices, rhythm patterns and so on, and the real time mode of operation means that any fill-ins etc. you insert during your performance are also stored in memory.

Alternatively, you can store monophonic melody lines (maximum 750 notes) either on top of an existing memorised chord progression or in isolation. This is done by pressing Melody record (switch 4) and Chord playback (1). As with polyphonic recording, any changes you may make in tone colour, sustain, vibrato and so on are recorded and stored in the menu's memory.

There are also two ways of changing the pre-programmed bass line contained within this menu, these going by the names of Auto Bass Edit (ABE) and Manual Bass respectively. In general terms, the former system is used for altering lines entered into the Multi Menu's memory in step time (either by the user or by the MK100's Japanese programmers), while the latter process must be adopted if the line was recorded in real time in the context of a stored chord or melody progression. A manual bass cannot be changed using the ABE, and vice versa.

Tape Interface

This final menu enables you to store sounds, rhythm patterns and chord melody sequences on ordinary cassette tape, thereby leaving space for further electronic fun within the memories of the individual menus. A tape recorder can be connected to the MK100 via the Tape In/Out jacks on the instrument's rear panel, and four of the Multi Menu push-switches take on the functions of Save, Load, Stop and Load OK respectively. Information takes about 80 seconds to be loaded, and LED indicators provide visual confirmation that all is functioning as it should be, so you can't really go wrong.


So that's about it! This new Yamaha uses a miniature keyboard that isn't uselessly small, contains some pretty reasonable factory preset voices, and above all, incorporates the Multi Menu system which allows the individual musician to take creative decisions for himself, and that, for me anyway, is what music is all about.

A technological monster of an instrument at an incredible price.

The Yamaha MK100 carries an RRP of £329 including VAT, though it is typically discounted to around £269. Further information is available from Yamaha MI, (Contact Details).

Note from ben@mu:zines:
A Kontakt emulation of the Yamaha MK100 that I developed is available via my other project - and available to purchase exclusively from KontaktHub.

Previous Article in this issue

Ibanez DM1100 Digital Delay

Next article in this issue

Spectrum MIDI

Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.


Electronics & Music Maker - Jul 1984

Gear in this article:

Keyboard - Home/Personal > Yamaha > MK100

Review by Vince S. Hill

Previous article in this issue:

> Ibanez DM1100 Digital Delay

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> Spectrum MIDI

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