A: This can easily be done using the Time/Pitch Machine in Logic. The first step is to determine how long the drum loop is in measures/beats. Listen to it, and count along to determine this. Next, make sure that the recording loops smoothly with itself. Open the Sample Edit window, and set it to loop play there. If you get a glitch free transition from the end of one iteration to the start of the next, then it is trimmed properly. If not, then adjust the end point of the region in the Sample edit window until it does loop smoothly. Most loops from commercial sample collections will not require trimming. Next, open the Time/Pitch Machine from the "Factory" menu in the Sample Edit window. Look for the line labeled "Length (Bars)". The number under the "Original" column for this line will show the length of the region, as it relates to the current song tempo. To the right of this, in the "Destination" column, you may set the desired length of the region, in terms of bars/beats. Set this to the length you determined the drum loop was when you listened to it by itself. For example, if the loop sounds 2 measures long, set the "Destination to "2 0 0 0". Next, click the "Process & Paste" button. The selected region will be time stretched or compressed so that it is the desired number of bars at the current song tempo. It is always advisable to start with a loop that is reasonably close to the desired tempo to start with. It usually works better to speed up a slower loop than to slow down a faster one, as it is easier for the Time/Pitch Machine to subtract extra samples than to add (interpolate) a large number of extra sample to lengthen a shorter loop.