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T1-99/4 Music Maker

Article from Electronics & Music Maker, July 1982

Micro Peripheral

Continuous eulogies on this or that advancement in digital synthesis techniques can seem dangerously like force-feeding if one isn't careful, and one (meaning those like myself with a tendency to get a little carried away at times) would do well to recognise that there are many people who are perfectly content with a less ambitious approach to computer music, and to whom a helpful, interactive music entry program with plenty of colourful graphics is infinitely preferable to the niceties of waveform sequencing and so on.

Just about every microcomputer on the market comes armed with some sort of music-making ability, courtesy of a sound generator chip buried in the bowels of its motherboard. The Texas Instruments-99/4 has the significant advantage of a 16-bit processor (9900) and it's also pretty cheap (ca. £300). That former fact would lead one to expect a reasonable degree of sophistication, but, ultimately, the musical output is only as good as the hardware actually responsible for outputting the waveforms. Texas Instruments are, of course, responsible for that games sound chip, the infamous SN76477, and the micro-controlled version, the SN76489. Bearing that in mind, you'd expect a better-than-average stab at music synthesis in their own TI-99/4. Their advertising certainly suggests this with "outstanding music/noise generation from 110Hz to beyond 40,000Hz". However, like its 8-bit bedfellows, the TI-99/4 uses a programmable chip that produces 3 channels of square waves with rather limited amplitude control (16 steps of 2 dB). Attempts to get inside the unit to dig out the identity of the sound chip proved futile (TI obviously believe in enforcing the suggestion of "no user serviceable parts inside").


Figure 1.

The software for the Music Maker comes in the form of a trendily-named "command module" which is nothing more than a ROM that slots into the front of the main console unit. The software is reasonably priced (around £35) and has both good and bad features (like just about everything these days). That's also true of the cosmetics of the system as a whole; whereas the main unit is very attractive in appearance (plenty of brushed aluminium), the power supply is an ugly, wedge-shaped thing looking a bit like a sewing machine pedal!

Figure 2.

On switching on the unit with the Music Maker module in position, you're ready to select between either TI Basic or the Music Maker program itself. With the latter, the first thing that appears is the logo (Figure 1) and some 3-part baroque-style music. The main menu gives three options (Figure 2): traditional mode, sound graphs, or load music. The traditional mode comes with a couple of staves as in Figure 3. Before entering notes, though, it's necessary to prescribe essentials (for this computer, anyway) like key and time signatures, and tempo. At the top right-hand corner of the graphics display, the particular measure that you're working with, is displayed. The number of measures available for a composition is a product of free RAM and note length. Thus, with 8K of RAM, 3 voices, and quarter notes (crotchets) as the minimum event time, 60 measures can be filled; with sixteenth notes (semiquavers) this is logically reduced to just 15. The right side of the display is used for selecting note/rest durations, draw/play/erase functions, and so on. All note entry is mediated by a flying cursor that's sent scurrying (slowly) around the screen with various arrow keys derived from a special overlay on the keyboard. Unfortunately, every time you want a different duration for a note, it's necessary to hop back to the right-hand side of the display to 'collect' a new note duration. Not surprisingly, this tends to slow down the whole business of entering music somewhat.

Figure 3.

The biggest limitation of this music entry program is the fact that you're limited to just 3 octaves from A2 to A5 (i.e., 220 Hz to 1760 Hz). Mind you, as the only audio output from the TI-99/4 is via the very small and rattling console speaker, this pitch restriction may be wise! It really does seem crazy advertising sound generation capabilities up to 40 kHz and not provide a decent audio output! Once one measure has been filled with up to 3 voices, you can then hear the fruits of your labour and progress on to the next measure. Fortunately, a copy facility is provided so that it's possible to repeat measures/parts from one bar to the next, or whatever, and this certainly helps to relieve some of the drudgery of the basic note entry procedure.

Figure 4.

Once you've got your notes in order, the entire piece can be played back according to the options in Figure 4. A useful feature is that as the music is played the computer displays the number of the measure it's currently playing — very helpful for pinpointing mistakes. Redo allows the user to select a repeat of the music as it's playing, but, unfortunately, it isn't possible to specify continuous repeats. Something that the Music Maker does do is to provide the option of printing hard copy of completed measures on a TI Thermal Printer. This is a very valuable feature, and, unlike the Mountain Computer Music System for the Apple II, which prints out music line-by-line, the Music Maker prints out measure-by-measure, and that makes a lot more sense. However, one has to put up with the unfortunate fact of life that a 5 x 7 dot matrix printer doesn't see quite eye-to-eye with the 8 x 8 graphics matrix used by the Music Maker program — and that means "that some of the characters in your composition may be only partially printed".

Sound Graphs

Figure 5.

Returning to the main menu, the other music entry option to consider is what TI call 'sound graphs'. According to the manual, eight noise generators can be engaged, with generators 1 to 4 representing 'periodic' noise and generators 5 to 8 white noise. To complicate matters, generators 4 and 8 play noise based on the frequency of 3. I have to admit that I got hopelessly confused with all this inter-generator interaction, and the final audible result tended to suggest that the software was a little confused as well. Still, in principle, you start off by selecting the frequencies that you want to play with by choosing 'discrete' or 'continuous' options. Whereas 'discrete' gives you a choice of 30 frequencies (Figure 5) with default values from 110 Hz to 1,976 Hz, you do actually have the option of specifying any frequency from 110 Hz to 20,000 Hz (the latter providing entertainment for one's pet pooches, I suppose). The 'continuous' option, on the other hand, although hardly in keeping with the true meaning of the word, does give a choice of 120 different frequencies, but these don't appear to be reassignable. After deciding which sound generator you're going to work with (Figure 6), the sound graph itself is alighted upon (Figure 7). As with the traditional mode of music entry, 'notes' are entered by using the various arrow keys. Each measure will accommodate up to three voices (in the 'freq' part of the display) and one 'line' of noise (in the 'vol' part of the display). Where all those 8 noise generators come in is beyond me and something that the manual isn't too clear about either. The good features of the Music Maker, i.e., the 'copy' and 'print' options, also work for the sound graphs mode.

Figure 7.
Figure 6.

That's basically it. You can, of course, save your composition on disk or cassette, or edit it until you're happy with your creative efforts, but the final proof of the pudding is only what the TI speaker feels like passing on into the ether, and the effect of that bit of hardware on the musical output of the TI Music Maker is about as subtle as drinking a glass of champagne with a mouthful of saccharine tablets!

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

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Electronics & Music Maker - Jul 1982



Gear in this article:

Computer > Texas Instruments > TI-99/4

Review by David Ellis

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