Yemaha TX81Z, courtesy of Audiofanzine. Note the small tab under the display, for the pull-out cheat sheet.
An FM synthesizer introduced by Yamaha in 1987. The TX81Z was a 1U high rackmount unit, with 8 voices and multitimbral capability, as well as a full MIDI implementation. Patch memory consisted of 128 factory patches in ROM, 32 writeable patch locations in RAM, and 24 slots for storing performance setups.
The TX81Z, like other of the less-expensive Yamaha FM synths of the 1980s, used the less desirable 4-operator voice setup ( as opposed to the 6-operator voices of the DX7). However, it used a new custom operator IC, the YM2414, which was the first one developed by Yamaha with sufficient computing power to do true frequency-modulation computations, as opposed to the phase modulation used by earlier models including the DX7. This meant that the TX81Z could use waveforms other than sine waves as its carriers and modulators; 8 choices were available. This more than made up for the missing two operators, and opened up new sonic territory for Yamaha's FM synths. Each operator had an ADSDR envelope generator controlling its amplitude. An LFO, which is assignable to control the frequency or amplitude of any operator, is available.
In multitimbral mode, up to 8 parts were available. Each could be set to a different MIDI channel, limited to a range of notes, transposed, have its output level set, and assigned to either or both of the two rear panel outputs (panning was not possible). A peculiar feature allowed notes to be assigned to parts in a round-robin fashion. "Effects" consisted of "reverb" (which lengthened the release phase of notes with short releases, to mimic reverberation), and "delay" (which repeated a played note at short intervals, a specified number of times, assuming sufficient voices were available).
The minimal control panel did allow patching editing (unlike the FB01), but it was difficult, using only up/down buttons and the 2-line LCD display. (An interesting feature of the display was that the startup message, displayed at power on, could be changed by the user.) Yamaha tried to alleviate the problem by incorporating a "cheat sheet" in the case, which could be pulled out through a slot in the front, and contained menu charts for which parameters were where. No one ever produced a programmer for the TX81Z, but within a few years of its introduction, the problem was solved by the advent of patch editor software, which the TX81Z's MIDI implementation supported nicely. Patches could be loaded and dumped via MIDI, or via a cassette interface. The TX81Z had the ability to load and convert patches from earlier Yamaha 4-op FM synths, including the DX27 and DX100.
Yamaha DX11, courtesy of Catawiki
About a year after the TX81Z's implementation, Yamaha produced a keyboard version, the DX11. Although it contained improved patch editing capabilities, the small size and Yamaha's aggressively low pricing of the TX81Z made it by far the more popular of the two. Today, TX81Z's can be readily found on the used market at reasonable prices, while the DX11 is hard to find. The TX81Z became a favorite of rap and house producers in the early 1990s, particularly for its factory bass patches.