The FP4 and the RD300 spec's.
RD-300GX: Digital Stage Piano
A Powerful Piano for Stage Performance
Specs
Keyboard 88 keys (PHA alpha II Keyboard) Sound Generator Conforms to General MIDI 2 System
88-key Stereo Multi-sampled Piano Sound Part 16 Maximum Polyphony 128 voices Wave Memory 128 MB (16-bit linear equivalent) Tones Normal Tones: 110
General MIDI 2 Tones: 256
Rhythm Sets: 5
General MIDI 2 Rhythm Sets: 9 Setups 32 Effects Multi-Effects: 78 types
Reverb: 6 types
Sound Control
2-band Digital Equalizer SMF/Audio File Player File Format Standard MIDI File: format-0/1, Audio File: WAV, AIFF (44.1 kHz, 16-bit linear), MP3
*Audio File can be played with Audio Key Function. Connectors Output Jacks (L/MONO, R): 1/4 inch phone type, DAMPER Pedal, Control Pedal, MIDI (IN, OUT), USB (MIDI, Memory), Headphones Jack: Stereo 1/4 inch phone type, DC IN Jack Others Rhythm Pattern 200 patterns Display 16 characters, 2 lines (Backlit LCD) Controllers Zone Level slider x 3 (Assignable), Equalizer knobs, Pitch Bend/Modulation lever, Assignable Switches (S1, S2) Internal Memory 1M bytes Power Supply DC 9V (AC adaptor) Power Consumption 11 W Accessories Owner's Manual, Audio Key Utility 2 Quick Guide, CD-ROM (Audio Key Utility 2, SONAR LE), Damper Pedal, AC Adaptor, Power Cord Size and Weight Width 1,444 mm 56-7/8 inches Depth 336 mm 13-1/4 inches Height 134 mm 5-5/16 inches Weight 16.4 kg 36 lbs. 3 oz. *The specifications are subject to change without notice.
FP-4: Digital Portable Piano
Fits in Small Spaces yet Performs like a Concert Grand
Specs
Keyboard 88 keys PHA alpha II keyboard Touch Sensitivity Light, Medium, Heavy, Off (velocity adjustable) Sound Generator GM2 system / GS / XG lite compatible Max. Polyphony 128 voices Tones 333 tones + 9 Drum Sets Effects Reverb, Digital Effect (62 types), Sound Control (3 types), 4-band Digital Equalizer Session Partner Rhythm : 80 types x 2 variations, Chord Progression : Automatic or input with keyboard (User Programmable) Recorder Tracks : 3 tracks, Song : 1 song (Max. 99 songs to Internal Memory), Note Storage : Approx. 30000 notes, Tempo : Quarter note = 10 to 500, Resolution : 120 ticks per quarter note Registration To Internal Memory : 24 x MAX. 25 sets Internal Songs 65 Songs Demo Songs 8 Songs Rated Power Output 7 W x 2 Speakers 8 cm x 12cm x 2 Display 7 segments, 3 characters (LED) Connectors Output Jacks (L / Mono, R) : 1/ 4 inch phone type, Input Jacks (L / Mono, R) : 1/ 4 inch phone type, Headphone Jack x 2 : Stereo 1/ 4 inch phone type, USB (MIDI) Connector, MIDI Connectors (In, Out), Pedal Jacks (Damper, Soft *, Sostenuto*) * Assignable, DC In Jack, DC 9 V (AC Adaptor) Power Supply DC 9 V (AC Adaptor) Power Consumption 22W Accessories Owner’s Manual, AC Adaptor, Power Cord, Music Rest, 2 screws for the Music Rest, Pedal : DP-8 (available Half- damper) Size and Weight Width 1,342 mm 52-7/8 inches Depth 305 mm 12-1/16 inches Height 135 mm 5-3/8 inches Weight 15.3 kg 33 lbs. 12 oz. Size and Weight ( FP-4 with dedicated stand KSC-44 and music rest ) Width 1,342 mm 52-7/8 inches Depth 341 mm 13-7/16 inches Height 940 mm 37-1/16 inches Weight 26.8 kg 59 lbs. 2 oz. *The specifications are subject to change without notice.
The RD can play midi files and wav files so you can play along with backing tracks and sequances. But the FP has some tricks as well. It has a function called session play which has pro standard backing tracks that can be played in any key and works like a top end arranger keyboard.