In Reason 7, Propellerhead added a new feature which allows you to change the timing of bits of recorded audio. This will allow you to correct timing issues right in the box without having to rerecord the audio. Let's look at how to do this. You can watch the video down below, or follow the steps under the video.
Step 1: You're going to want to double-click on the audio clip in the sequencer that you want to transpose. This will bring up the option we need in the next step. Step 2: After double-clicking on the audio clip, you need to choose a Stretch and Transpose Type from the drop-down menu. This is extremely important because if you don't select the right one, the quantized audio will not sound natural. Select Allround if you're going to quantize an audio clip that has several instruments in it or an audio clip that has one instrument but is playing chords, select Melody if you're going to quantize an audio clip of an instrument playing a melody and select Vocal if you're going to be quantizing a vocal.
Step 3: After you've selected the Stretch and Transpose Type, you can go ahead and quantize the audio clip. You should see little markers throughout the audio where Reason detects a change in the note. Make sure that Snap at the top is not checked (unless you want the notes to snap), and go ahead and drag the markers to the appropriate place. NOTE: Another option is to right-click the audio track and select Quantize. This automatically moves the markers to what Reason feels is best. Of course, this method is not always 100% accurate, which is why I recommend doing it the manual way.
Step 4: Listen to the quantized audio clip and adjust as necessary.