Roland PB-300 Rhythm Plus

Sixteen choices, one player

Eight rhythm buttons and a bank selector gave the PB-300 sixteen starting points, from Rock and Disco to Waltz, Bossa Nova and Enka. Beside them sat a large tempo knob and separate level sliders for rhythm, bass and chord or arpeggio accompaniment. The controls brought the decisions close to the musician's hands.

The fill button gave those preset rhythms a little room to breathe. Press it during playback and the fill arrived in the following measure. Press it before starting and it supplied a one-measure introduction. For regular changes, a selector could insert a fill every two, four, eight, twelve or sixteen measures. Rhythm Break let the player drop the percussion out and bring it back.

These were ways of shaping a performance while it was happening. The patterns were already there; the pianist decided when they should enter, change or leave.

The rear panel offered another way to make those decisions: separate pedal sockets for Play/Stop and Fill In. Roland's manual shows the HP-300/400's soft pedal connected to the rhythm box and also lists the optional DP-2. A pianist could call for a fill without taking a hand off the keys. A rear-panel Accent Level control adjusted the emphasis of the rhythm's accents.

Two instruments making one accompaniment

The PB-300 supplied its own percussion and bass sounds. The chords and arpeggios sounded through the connected HP-300 or HP-400 piano. MIDI carried the musical instructions between them, while the audio connections brought their sounds together.

That division is central to understanding the instrument. On the HP-300/400, the keyboard split between F-sharp and G below middle C. The lower section supplied the notes that guided the automatic accompaniment; the upper section remained available for the pianist to play. The manual specifies chords of up to four notes and places the generated chord or arpeggio two octaves above the keys pressed. The held keys served as instructions rather than sounding that chord directly. With HOLD engaged, the accompaniment continued after release, until a new chord replaced it.

Chord and arpeggio were alternative modes. One supplied the accompanying chords; the other broke them into moving notes. Their variation switch offered two patterns, while the bass had three, matched to the selected rhythm. The Nuance switch added another connection to the performance: the force of the pianist's key attack could influence the bass and chord or arpeggio levels. It was not a facility for individually programming the drum sounds.

Synchro Start made the first entrance part of the keyboard performance too. Once armed, the PB-300 waited for playing in the lower section before starting its rhythm and selected accompaniment.

The recorder joins in

Adding the PR-800 changed who led the system. With the PB-300 set to external clock, the recorder's tempo and transport took charge. The rhythm box's own tempo knob, Play/Stop and Synchro Start no longer controlled playback in that arrangement.

The rear-panel connections reveal how carefully these companions were meant to fit together. MIDI carried control information. A separate MIX IN could accept an external sound—the manual illustrates the PR-800's metronome—and combine it with the PB-300's rhythm and bass at the output.

A contemporary listener

In his August 1984 review, Geoff Twigg judged the PB-300 within the Piano Plus system and against his own expectations of a drum machine. He found it useful beside the piano, but wanted more programming freedom. Its tempo knob also lacked a numerical BPM display.

That response gives the machine a useful contemporary perspective. Its appeal depended on what the player wanted to do: sit at the piano with a responsive accompaniment, or construct a drum part from individual decisions.

Other ears for an old companion

The PB-300 later found listeners outside its original piano setting. CORAL D released a collection of recordings of its rhythms in 2021. Solvent identified one in his studio. Those accounts extend its musical life beyond the home-keyboard system pictured in the early press.

Other owners went further. ESTECHO documented a four-output modification: bass drum, snare, a toms-and-clave group, and cymbals and hi-hats. It repurposed the pedal and MIX IN sockets; the author had not tested the bass accompaniment. Zack's separate CPU project added individual MIDI triggers, but his December 2020 account says it had no pattern support and that the code could no longer be found. These were altered instruments, with different capabilities and compromises—not features waiting to be discovered on a stock PB-300.

The PB-300's particular charm lies in that original relationship with a player. A left-hand chord, a fill queued for the next measure, a rhythm brought in under the melody: small actions that let a preset accompaniment take part in a performance.