146 CHAPTER 3 Intermediate Sequencing Techniques to be time-stretched to follow the tempo changes. Time-stretching requires the computer to calculate and adjust the samples of the audio files according to preprogrammed algorithms present in your sequencer. The sequencer will construct the new audio file according to the original tempo of the file and the desti- nation tempo. In most sequencers this action can also be done in real time by simply clicking and drag- ging one side of the audio region (e.g., DP and PT). By using different synchronization protocols we can have different devices and machines running together in perfect sync. While linear machines (meaning tape-based devices, such as multitrack tape recorders and video machines) can use a protocol called SMPTE to achieve synchronization, non- linear machines (sequencers, drum machines, HD recorders, etc.) can be synchronized using either MIDI Clock or MIDI Time Code. These two protocols, which both use the MIDI network to send synchronization messages, require one device to be set up as master and the others as slaves. In the case of MC (which is a tempo-based protocol) the same message is sent 24 times for every quarter note. Through the use of an additional message, called Song Position Pointer (SPP), the master is also able to describe its position in the sequence by counting the number of 16th notes that passed since the beginning of the project. MTC is a real-time-based protocol that derives from the original SMPTE set. They both describe the passing of time in hours:minutes:seconds:frames. MIDI messages are sent each quarter-frame to describe the exact position of the master device. As soon as the slave devices receive the starting position, they will move to it and start playing, continuing as long as they receive MTC messages. Frame rates for both SMPTE and MTC include 24, 25, 29.97, and 30 fps. Two extra rates, called 29.97 drop and 30 drop, exist. While the latter is rarely used, the former is utilized to make up for the discrepancy between the video NTSC frame rate of 29.97 and the 30 fps rate used by broadcasters. Backup and archiving sessions are crucial to the safeguarding of your precious creative work. Backup sessions are conducted during the realization of a project as quick, overnight copies after each working session. When a project is finished and you don't plan to work on it again for a long time, you will archive it, meaning make a copy on a separate medium (CD, DVD, etc.) and delete it from the original working HD. Software that can help in the process of backing up and archiving can be divided into synchronization applications and backup/archiving applications. The former keep a perfect copy of the current project on the main working HD and another medium (usually another HD), and they keep track of the latest modified files in both locations. The latter create a copy in a proprietary format (usually compressed up to 50%) that can be accessed only by restoring it onto an HD via the same software used to back it up. Media that can be used to back up and archive are HD, CD-R/RW, DVD / R/RW, tapes, and Blu-Ray DVD. No matter which system or media you use, remember to back up often and to keep several backup/archive copies of your most important projects. 3.13 exerCISeS Exercise 3.1 Set up and record a sequence with the following features: a. Fourteen MIDI tracks b. Instrumentation: drums, bass, guitar, keyboards, percussion, five horns, strings c. Tempo of your choice.