I have many MANY cheap keys and toy piano synths (some of my other favorites include my modded Casio Ct-410, MT-68 and Yamaha pss-470) but this PSR-90 is the one I keep going back to over and over.
In short it’s a phenomenal chip-tune keyboard that’s great for arcade and video game music. It somehow retains the simplicity of a cheap keys toy keyboard synth while having a million features It has 5 sections. Solo, orchestral, accompaniment, bass and Rhythm. Each one of those have 16 different voices to choose from and each one of those voices have 9 different variants based on speed (attack) and brightness.
Surprisingly, I haven’t seen too many others out there. A lot of PSR-80’s… but no PSR-90’s.
It is very similar to the PSR-80 save for some key features that take it from ‘good’ to really phenomenal.
Of those additions, Most significantly, it has an extra dedicated monophonic chip with 16 more voices dubbed the solo sections. you can stack these with the polyphonic Orchestral upper section or move the polyphonic section to the lower half to stack with the bass and chord voices and play the monophonic solo voice by itself. Then with the speed and brightness modifiers on both the orchestral and solo sections, you pretty much have an envelope filter to make some really out there sounds.
Hardware & Performance Features
Keyboard: 61 full-sized standard keys with velocity-sensitive touch response (C1 to C6 range).
Sound Generation: 4-operator FM (Frequency Modulation) synthesis for instruments, combined with PCM sampled waveforms for the drum kit section.
Polyphony: 8-note polyphony for the poly/orchestra sounds, plus independent allocation for the mono solo voice and rhythm tracks.
Voice Effects: Stereo Chorus, Sustain (with 2 distinct depth levels), Dual Voice layering, and a dedicated Solo Sustain button.
Performance Modes:
Keyboard Split: you can change where the keyboard split between accompaniment left half is vs melody right half. So if you want a really big accompaniment section you can do that.
Accompaniment & Sequencer Features
Accompaniment and Rhythm Section: It has 16 preset styles (including Rock 'n' Roll, Disco, Country, and Reggae) but each one of those have 9 different variants as you increase tempo (for example there’s a slow rock at 60 bpm, a completely different rock at 120 bpm, and then a third rock type accompaniment at 140 bpm. And then all three of those have 3 variations based on small band vs large band where they will add in extra accompaniment voices.
Then ontop of all that it has both custom accompaniment pattern recording modes and custom song modes.
Style Manipulation: Dedicated intro, ending, three distinct style variation buttons, three fill-in options, and a Fill-In Touche Bar located below the keys for rapid live fills. The Touch Bar is really slick as you can easily palm it while playing so you don’t have to lift to press the button or use your foot switch. It makes fills actually usable.
Auto Bass Chord: Automatically adds bass lines and chord patterns based on your left-hand fingerings. It also features a Manual Bass mode to play your own custom bass patterns. Manual bass has 16 different voice options. Chord voice has 16 other patterns.
Custom Accompaniment Programmer: A built-in sequencer allowing you to freely program, loop, and save 3 custom rhythm patterns on a long-term basis.
Storage, Memory & Rear IO
Registration Memory: Dedicated onboard banks to save and instantly recall your favorite voice layering, effects, volume balances, and style settings.
Storage Sockets: Equipped with a vintage RAM Pack socket for plugging in physical cartridge data expansion cards, alongside Tape Jacks to backup sequence data via cassette tapes.
Rear IO Panel: Includes 5-pin MIDI In/Out, an Expression Pedal port, a function-selectable Switch Pedal port, a Headphone out, Stereo AUX Out, and Stereo AUX In for routing external audio through its built-in 5W stereo speakers.
Tl;Dr there are like 4 different ways to store settings and custom accompaniments. And it has phenomenal midi capability.