We can put it this way, the only thing piano and organ has in common is the keyboard - or manuals like we organists like to call it.

Some basics tips and advices.
1. Sound production of these instruments are very different. Piano uses hammers to strike strings, but (real) pipe organs produces sound by blowing air into and through pipes.
2. Piano is only one voice, but organ has anywhere from 1 voice (called stops) to 200+ voices/stops.
3. Stops are marked 32', 16', 8',4',2' etc. - 8' is the same pitch as piano (middle c on piano is middle c on organ is middle c there too if it's played with 8' stop). 32' sounds 2 octaves lower, 16' sounds 1 octave lower, 4' is 1 octave higher, 2' is 2 octaves higher, 1' is 3 octaves higher.
4. Stops are like orchestra, there are woodwind/brass/strings stops. Brass stops are called reeds. The foundation stops of the organ is the principal family if you use that family plus stop called Mixture you can make lot of noise but still be safe because those blends well. If you want more noise then add some Reeds but stay away from those stops you have 1/3 etc. markings on them - if you want to be safe

5. Playing style on organ is a lot depending on the accoustics of the church/hall - you don't have sustain pedal to save you if the accoustic is bad. Example: In large Cathedral you would play fast passages non-staccato and in extreme cases staccato to stay away from muddy sound.
6. On real organs, doesn't apply to electronic organs, you need to press the notes ALL THE WAY DOWN and take them ALL THE WAY UP!!! If you do not, you won't get pretty sound!
7. Key attack is various between organs some organs are have light attacks but some are really heavy if you pull out many stops. Again doesn't apply to electronic organs.
8. Stops respond variably the bigger pipes need obviously more time to respond than the smaller one so if you pull out 16' stop or even 32' stop you need to be aware of this fact. specially if you're playing some fast passages. Doesn't apply to electronic organs.
9. Play legato! It's better to think about playing legato while you're getting used to the organ and it's behaviour. Legato legato legato!!! Don't even try to play staccato yet. This applies mostly on real organs not the electronic ones, but still keep it in mind.
10. The manuals (keyboards) have names by position. On 2 manual organ, the lower manual is called Hauptwerk or Great Manual the top one is called Swell because the stops are in wooden box which can be closed/open. On 3 manual organ normally the middle manual is the Hauptwerk and the top manual is the Swell, the lowest manual is called Ruckpositive or Choir in English. The 4 manual is called Solo in English and the 5th is called Echo in English, those two are the top ones. So the layout in 5 manual organ would be ECHO, SOLO, SWELL, GREAT, CHOIR.
Hope this helps, now where's my bed.

Btw. feel free to ask if you need some more info.

falcon1 - yup, I'm organist
