The PSR 420 is a 5 octave stereo touch sensitive keyboard with 128 GM voices 8 drum kits and 100 Rhythms.
The 420 includes a registration feature which stores front panel settings that you have chosen for a voice. It has effects such as sustain and ambience -but these are not much of an enhancement to the basic voice. Voices can be layered and split,allowing up to three voices playing simultaneously from the keyboard. Voices can be harmonised when auto accompaniment is on and there are variations which help the harmony match style of rhythm.
There is an on board sequencer which holds 3 songs and a ROM cartridge slot which adds songs and styles and registrations,though cartridges maybe hard to come by.
The keyboard is tunable by Octaves and so the range of a voice can be offset by an octave from the main voice which is transposable in semitones,this is good when layering as the second voice needn't be in the same octave as the main voice.
The 420 supports System Exclusive dumping,but curiously uses a two fold approach- there are two SYSx files and initial dump followed by the main storage - and these can be saved independently. I am not sure what Yamaha were doing here - usually the idea is to save the whole internal memory of your machine.The INIT dump maybe to send settings to sequencers to preserve the current front panel status. Programs such as MIDI-ox will allow PC connection to the SYSx facility.
There is an 8 track mixer which has a bar graph indication of the volume of the sections playing and also you are able to mute the tracks or change what voice is playing back. The accompaniment section can be rendered small or large scale and can respond to either the lower or the whole keyboard.
There are two modes for auto accompaniment - fingered or single. Single plays the chord from one key and fingered has you choose the chord manually.
The song sequencer has a repeat section facility so you can practice given bars of music over and over again - the slight problem being that the looping leaves a gap before repeating,so this throws your timing out.
The 420 has a couple of Yamaha type features which are rather peculiar - OTS and "Minus one" and "Accompaniment Freeze". The Freeze button holds onto the current Accompaniment setting when recalling registrations - but I have found it a pain to remember when to press this and when not.
The minus one mode turns off one or both of the parts played by a demo song or cartridge so you can play it yourself - such features are really in the domain of a beginner or organist and do not really suit keyboardists and synth players.
OTS is One Touch setting and sets all the parameters to match the current style - so if you are playing country you may get a steel guitar and if you are playing a ballad you may get a sax.
Local control for MIDI is supported meaning that you can disconnect the keyboard from the sound generating system,which enables playing through a PC for recording/playback with music software.
There are MIDI IN and OUT ports but no THRU - a Sustain jack and for better or worse the headphone socket is on the front left side rather than the rear,this is good if you don't want your phones cable trailing over the keyboard,but bad if you want a LINE out connection at the rear and find you have not got one.
PSU is 12v and the polarity as always is opposite to CASIO machines,so don't use a CASIO PSU for Yamaha or vice versa.
Good Points: The keyboard includes a GUIDE system which stops the play and waits for you to press the key when playing back a song,also indicating which key to press on it's LED display above each key - this makes learning songs quite easy.
The effects pads generate little snippets of drum flambes or noise effects as opposed to having drum pad keys - the drums can be triggered from the keys anyway - or just in the split section,and the effects vary the pitch according to what chord is playing in the accompaniment.
Touch response is good and also adjustable - it shows how effective it is when used with the Grand Piano which is perhaps Yamaha's forte - so to speak.
Niggles: There is no pitch bender - which is kind of odd for a keyboard which supports pitch bend - but then the whole idea of the model number is to clue you in to which parts were sacrificed to improve the cost - the pitch bender you get on the higher model numbers.
The LCD display is not backlit which means you cannot see it in the dark.
Time Sync pulse on the drums is generated and responded too- however the start/stop signal is not generated - which makes synchronisation a real pain.