After his musical training with Erich Ackermann in Fulda, Germany, Rübsam studied at the Musikhochschule in Frankfurt am Main with Helmut Walcha.
Additional studies in organ followed with Marie-Claire Alain in France and with Robert T. Anderson at Southern Methodist University in Dallas, Texas.
He won the first prize at the International Organ Competition in Fort Wayne, Indiana and the Grand Prix de Chartres for interpretation in 1973.
In addition, he has recorded a major part of the keyboard works of Johann Sebastian Bach on modern Bösendorfer pianos and the lute-harpsichord.
He is sound engineer and producer for the Naxos Organ Encyclopedia Series and has been in great demand as concert organist and jury member for international competitions.