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Buy used. The best organs are vintage analog electronic organs. In Cleveland today there was a Hammond A105 for $500. An excellent deal considering it is a Hammond B3 in a home console with internal speakers. Hammond B3's are very expensive. They were made from 1955 until 1975. The better years are the early 60's models IMO. Maybe you are not partial to the Hammond approach to organ making, but there is something very special about the Hammond sound and the electromechanical approach to tone generation by use of tone wheels spinning in front of electromagnetic pick-ups give the organ a very smooth natural sound. The idiosyncrasies in the design produce various artifacts in the sound. Hammond saw these as flaws and tried for years to remove them, but 'key click' and 'cross talk' gave the Hammond it's special character.
Hammond made organs other than tone wheel organs. Before 1975 most of their non tone wheel, fully electronic models were entry level instruments designed to compete with the lower priced organs of their competition. The truth be known, the competition had them beat hands down in this department. Where Wurlitzer, Conn, Gulbransen, Lowrey, Thomas, Baldwin, Kimball, Allen...and a couple others all spent much R&D developing innovative quality voicing and features for their vacuum tube, and eventually fully solid state organs, Hammond had nothing in the full pedal console except the Hammond Concorde. I recommend avoiding most Concorde models, especially the earlier ones.
While on the subject of electromechanical design, Wurlitzer also used such a system from 1946 until 1961 that produced excellent tone and dynamics. These were Electrostatic Reed organs (ES reed for short). You can read about these organs and hear examples (links below), but to play one in person is the ultimate joy! Their are two varieties of electrostatic reed organs that Wurlitzer produced. Keyed Reed and Free Reed. Simply put, the first ES reed organs were better suited to classical organ music and many classical purists have endorsed the Wurlitzer keyed reed models because they have excellent pipe like tone and the notes even have a slow onset due to the keyed reed action. Keyed reed models include all models 50 and below except 44. Free Reed organs were Wurlitzer's answer to the tremendous success that Hammond was having winning over the general public. Part of what made Hammond organs appealing to the fans of popular music was that Hammond tone wheel response was instant. All 91 of the organs tone wheels spin continually from the moment the organ is started so that when any key is pressed the note has an instant attack. The seeming sluggishness of a pipe or reed building up simply isn't responsive enough for most popular music, even in 1935. So by sealing off the reeds from acoustic audibility from outside of the cabinet Wurlitzer was able to apply air to all of the reeds at once. From the moment the organ was turned on, all reeds are creating tone. Since the reeds are used electronically and not acoustically in an electrostatic organ this method of blowing all of the reeds at once proved very successful. To simulate the slow onset of the keyed reed there is an ATTACK tab, flip the attack off and the notes then come in slower, which is ideal for classical and slower hymns. The Free Reed models are 44, 4410, 4420, 4430, 4600, 4601, and 4602
Both Hammond and Wurlitzer electromechanical organs are very reliable! Vacuum tubes and electrolytic capacitors are easy to access and change. All parts are still available either NOS or quality used.
I have explained these two organ types in depth because in my opinion, if you don't start out with this type the chances are very good that you will 'graduate' to this type because of it's superior performance.
My recommendations for organs other than the electromechanical choices above are:
Highly recommend are darker
Hammond Colonnade, Hammond Elegante, Hammond Aurora Deluxe
Wurlitzer 4500, Wurlitzer 4300,Wurlitzer 625 or 625t, Wurlitzer 630
Conn 541, Conn 542, Conn 543, Conn 545 Nasau, Conn 553 Trinidad, Conn 554 Trinidad, Conn 650
Gulbransen ( typically known for model names more than numbers, but have numbers)-
Pacemaker,President, Riviera,Premiere,Rialto K, Rialto II
Thomas- I love Thomas organs! I have 2, but I can't recommend as an only instrument. They don't have much ensemble effect and this could detract from hearing quality results early in learning, but once you become a pretty good player the Thomas organs are incredible to play because each voice is pronounced and unique.
Baldwin HT2, HT2R...and some others...I'm getting tired (lol)
Allen ( others can recommend better than I)
Rodgers ( ANY!)