No need to use samples or physical modelling of some sound if instead of digital imitation or sample of sound real acoustic sound is used. There is electromagnetically prepared piano, and magnetic resonator piano, and its newbuild version 2019. All three are almost the same. Then is VO96 acoustic guitar synth that is suitable for other string instruments also. And Krzystof Cybulski: “Acoustic harmonic synthesizer”. Such design can use any piano like keyboard with strings. Clavichord, Harpsichrod / Cembalo, Spinet, Or rare instruments like Lautenwerk, Viola organista / Geigenwerk, or hybrid instrument like Omniwerk, Hammerspinet, Celestaphone. “One becomes twenty - a unique hybrid piano”, and Piano lutheal. Such instrument can be called “synthclavier”, it is clavier (keyboard / piano) and acoustic synth. VO96 style electronics can be connected to zither or harp, harpeiji, or thumb piano like array mbira, kalimba, or cimbalom. There is also guitarpiano, piano that sound like guitar. This synthclavier can have display and touchscreen, and similar system that player piano has, keyboard plays itself using mechanical system. Now sequencer can be added. Display can show sound information like synths do. There was Orhestrion / Photoplayer instruments, that imitated whole band or orchestra. Similar can be build nowadays also. Valve instruments like trumpet and trombone connected to some pneumatic or hydraulic or electromechanic system that plays those horn instruments. Also old theatre organ / dance organ type reed organ / positive organ / pipe organ system can be included. Hammond organ was designed to compete with theatre organs have similar sounds. So complete instrument is combination of electromagnetically prepared string instrument (piano etc.), free reed organ and pipe organ and horns like trumpet, trombone etc. that have valves. Even saxophone has horn version, saxhorn. Cheap plastic reed organs like Bontempi type can be added, each rank of keyboards is different sounding complete simple reed organ, one rank is magnetic piano, one is for theatre / pipe organ sounds, and one rank for horns used with remote control hydraulic or pneumatic or electromechanic system, when player plays some note in keyboard that note is played by trumpet or trombone etc. when computer controls this remote playing system. Even polyphonic aftertouch can be added. Now complete acoustic soundmachine, like acoustic synth, is possible. No samples or physical modelling of acoustic sound, but real acoustic sound.
If modern version of Orchestrion / Photoplayer is made, it needs bells / chimes also, like Deagan Una-Fon in 1920s. Bells/chimes are remotely controlled, player presses key and some electromechanical system plays bell. Instead of playing Yamaha DX7 bell sound player plays real acoustic bell. In previous post was “keyboard ranks”, that meant keyboard manuals, not “ranks”. In multi manual organs, organs can have 10 or more manuals, and in each of those keyboard manuals is several ranks for pipes etc. Magnetic resonator piano is large instrument, but piano has also smaller designs like mini pianos and even toy pianos that have good sound quality and there is foldable pianos that are portable. Piano can also have pedalboard, pedal pianos. So “Synthclavier” can be small and light also. And not restricted to piano design, any keyboard stringed instrument will do, and there is large amount of them in different designs and forms. Lautenwerk was piano lute, clavichord gusli is keyboard zither. and guitarpiano was mentioned already. Some kind of hybrid instrument, like Piano lutheal, Omniwerk or Hammerspinet is suitable to magnetic resonance action, so that hardware has many sound properties. Also there is pocket trumpet, miniaturized trumpet that has almost the same sound as real trumpet. Such small and handy instruments are suitable for Orchestrion, they do not need much space and are light. Several modern “acoustic synth” ORchestrion models can be made, some are light for gigging musicians, some can weight several tons. Number of organ pipes can vary and their size also, free reed organs were used as church organs also (Holt organs etc.). Hammond organ was made to imitate dance / theater organs, that s why they have drawbars (organ ranks). Reed organs have ranks too, those models that were used in home. Newer models had electric compressor for blowing air. Cheap toy organs had electric blowers also. Several of those reed organs, with different tonal characters and sound can be collected as one 10 manual or more instrument, each manual is one individual reed organ. Pipe ranks and reed organs can use all same electric blower so it is simple, only plastic air tubes go to reed organs and pipes. Including bells, horns and keyed strings (those using electromagnetic resonance) instrument can play many sounds. There is things like Gamechanger Audio Motor Synth, Folktek Mobius Harmonizer, American Keyworks Thorium AK-24, Ableton loop netpage “Build your own acoustic synth” (those two like one string electric guitar), and “The Tine Organ” Matthew Steinke, but those seem to be electrically amplified, so sound comes through some pickup like guitar pickup, when acoustic instruments must use acoustic microphone to record sound, and acoustic instruments are searched here.
There is also “Magnetic resonator guitar”, that and VO96 and E-Bow are almost same. Lots of stringed instruments can use them, autoharp, harpeiji, array mbira etc.
Perhaps nothing to do with synth but there is “Hammerjammer” guitar gadget, Kalimbatar - kalimba guitar, and someone has build mbira guitar. Those are basically polyphonic instruments. So now guitarist can play guitar (or guitar / thumb piano hybrid) polyphonically, and guitar can have many sounds at same time, five instead of just one note at same time? This is one way to build polyphonic instruments.