The metro (metronome) object is the most obvious way to trigger repeated events in Max. Repetition is, of course, a key component of most music (and most time-based art in general), and the metro object encapsulates the whole low-level process of a) cause something to happen, b) schedule the same thing to happen at some future time and repeat the process. The only thing it needs to "know" is what time interval to use for its repetitions.
A single sfplay~ object can refer to many different sound files, or even specific portions of sound files, with a unique "cue" number assigned to each sound. Once those sound cues have been preloaded (i.e. taught to the object), you can cause the object to play a cue just by sending the desired cue number in its left inlet.
This example demonstrates creating a RAM buffer to hold a 10-second stereo recording, recording live audio into it (with input volume adjustment), and then playing randomly chosen backward clips of that sound, with a trapezoidal window to taper the beginning and ending of each clip to avoid clicks.
This example shows one way you might use phasor~ to make the length of an audio sample loop stay precisely synchronized with the beat of the transport.
The MSP phasor~ object is frequently used as a low-frequency control signal for audio. Because it is often used to control other signals over a specific period of time, phasor~ can use tempo-relative timing, too. The frequency (rate) of a phasor~ is normally specified in Hertz, but you can alternatively give phasor~ a time interval, using tempo-relative time units, and it will use the inverse of that to determine its frequency.
This abstraction encapsulates delay, gain control, and stereo panning in a single object that can be used in some other "parent" patch. It assumes that its first inlet will be connected to a tapin~ object in the parent patch. That tapin~ object will send a tapconnect message when MSP audio is turned on, thus linking the tapout~ object in this abstraction to the memory buffer of the tapin~ object in the parent patch.