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This will typically be a separate track in your software. Depending on how fast or slow you want the song to be, the speed of the click can be divided into halves, thirds, or quarters. You can experiment if you’re unsure.  The click track will help to ensure that with all of the copy and pasting you’ll do, the song stays on tempo. Your tempo will vary according to the mood and style of the song, and is typically between 80 and 120. More likely than not, you'll turn the click track off once you have a basic beat made -- this is just a guide right now to keep you on tempo. The drums are your backbone, providing the structure that all other instruments fall on. They usually come first. That said, you don't have to use drums for percussion -- gunshots, car doors slamming, synth blasts, pots and pans, and much more have been used to provide rhythm in songs of all genres.  Hip-hop beats have a classic trio -- kick drum, snare, and hi-hat. That's it. Check out DJ Premier's famous beats on the album Step in the Arena for a classic example.  You can download drum packs, which are recordings of different percussion sounds, to use in your songs for free online. Search the drums you want on a search engine, like "Steel Drum Sounds Pack," or "Led Zeppelin Drum Sample Pack." Together, the bass and drums form the rhythm section of every song. While the drums set the tempo and beat, the bass locks into this rhythm and hints at the melody, often with simple, danceable lines. There are many songs that are almost all drums and bass -- so don't disregard the bass because it is harder to hear in the final mix -- it's the instrument that gets people dancing.  Bass lines can be a simple, like Nas' "Memory Lane (Sittin' in the Park)," or complex, like Common's "Be (Intro)." A bass line doesn't need a bass guitar, though they help. Listen to what Daft Punk is able to do with deep synthesizers for another example. Your bass line and kick drum (the deepest sounding drum) should mesh for the maximum effect. Most producers like to have them alternating. The bass and the drums should be unique to make your song unique. Still, the melody line is where most songs come to their own and become new, big beats. Build melodies around your mood, using synths and electronic sounds for EDM or techno music, horns and guitars for R&B, even odd "found sounds" from weird sources (see "Windows Media Player" by Charles Hamilton for an example). The possibilities are endless. Play around with sounds constantly-- the only way to find out what sounds best is to try out as many different orchestrations as possible. Looping is taking at least one bar of music, like a drum line, and repeating it flawlessly so it sounds like the drummer is playing the exact same thing the whole song. You can, and should, loop everything -- making the perfect smaller section and then dragging it out to save time and get the perfect tempo for your entire beat. Great loops don't feel like loops -- they perfectly come back around so it sounds like a real musician is playing the instrument over and over again. A straight beat is great. But most songs are made up of several related beats, each coming together to provide excitement and movement. The new beats, however, are almost always closely related. Some ideas for breakdowns and changes include:   Add a new melody line: A new sample, some brief vocals, or the re-emerging melody line usually signals a "chorus" or sing-along section of the beat. This is usually the most memorable part of the beat.  Drop to a minimal beat: Dropping to just drums and bass, or even just drums, is a great way to lower the energy. You can then blast the beat back to pump the song back up and get the crowd really moving.  Building and dropping: Add volume, new instruments, and drums to grow tension and energy, then drop out to a big, bassy, and danceable section. These are more nebulous concepts of music composition, and every producer has different preferences. No matter what you choose, think about these three concepts to make interesting, layered beats.   Tension: Found in juxtaposition, tension is what pulls the song forward. It is the difference between the intense moment before a "drop" in dubstep and the cathartic, slower boom after the drop -- this difference creates tension, which creates greater songs.  Energy: What is the tempo of the song? How does it change or evolve, and does it bring the crowd with it? Some songs need full energy the entire time, plowing ahead. Others songs benefit from slow builds, changes, and swings in energy.  Space: What is the beat for? If it is for a rapper, you best leave some moments of near "silence" so that they can get the words out. Think of how "full" your ears feel -- sometimes simpler is good, allowing one instrument to shine. Sometimes you need all 30 tracks at once.
Set up a metronome or click track to get the beat started. Build the drum beat before anything else, meshing it to the click track. Use the bass line to set a melody to the percussion. Add in melody instruments, sounds, and lead lines. Practice using seamless loops to extend your song out. Mix up the song with a "new" beat in the intros, outros, and/or middle. Think about tension, energy, and space when building beats.