I have a problems with midi keyboard and multiple tracks

I am new to Reaper and the world of DAW. Whenever I create multiple tracks, it will sound like a crack when I try to play them via midi keyboard. What happens is, instead of one armed monitored track being playout, the other (disarmed and monitor-off) tracks somehow also played out. The sound of other tracks are like a cracked sound. I don't know why this is happening, but when I set the I/O of each track to send/receive all the other tracks, this problem is gone. However, recently another problem occurs. The midi control channel that I set for one track also control another (maybe this is because track is set to send/receive?)! So I deduce that somehow my midi keyboard is connecting to all tracks one way or another (I tried remove all the midi-input of other track except the one I am using, but this didn't solve) PS: I am using windows 7 x64 with Reaper x64 and M-audio Prokey 88 with ASIO4ALL EDIT: I think the problems lies with sfz player x86 (Soundfonts somehow conflict each other??)

Try changing SFZ Player's memory mode.

I tried all the memory options but still isn't working. Whenever I press play, the program will automute everything because the track sound are over the limit.

The problem lies with your routing. Click on an I/O button and look at the bottom part of a send or receive. On the left you'll see where the audio is going, and on the right where the MIDI is going. Now you've set up your tracks to send to all the others, so what happens? Let's say track 1 is armed and it's sending to tracks 2 and 3 and all three have sfz player on them. Well, track 1 plays, but the MIDI is also sent to 2 and 3 so they play too. So far so good, but track 1 is also sending its audio to tracks 2 and 3 and meanwhile track 2 is sending its audio and MIDI to tracks 1 and 3, and so on for track 3. Each track is now playing the sum of all the tracks and all are feeding the Master track. That's one hell of a lot of noise :D, and lucky you hadn't enabled feedback or we might have seen your speaker cones launched into orbit. The solution, kill all the sends you don't need. With multiple tracks like this I set them to automatically arm when selected. You'll find this option when you right-click the track's record button. Then to audition an instrument I just select the track it's on and play. Oh, and remember to turn monitoring on too. HTH Steve

What happened is when I make each tracks to send to all other tracks, the problem is gone (the noise problem). However, when I turn that off, the problems appears.

Perhaps you could compress a simple problem project file (no audio samples needed) into a ZIP file and post it here as an attachment so we can have a look at it and see what's (not) happening? In XP, right-click the project file, select Send To ... compressed (Zipped) folder), drag your reaper.ini file into the ZIP file (You should be able to get to the (hidden) folder containing the file from [Options] > select "Show Reaper resource path in Explorer/Finder") when you reply, scroll down a bit, open the "Additional Options" section if needed by clicking the double downwards arrows, click on [Manage Attachments], browse to your ZIP file, select and Upload it. You will also find it helpful, in "Folder Options" (on a Windows PC): -- to Show Hidden Folders and Files -- to Show File extensions (or you are vulnerable even to the most simple double-extension trick to disguise malicious files)