Pulses per quarter note

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Pulses per quarter note (PPQN), also known as pulses per quarter (PPQ), and ticks per quarter note (TPQN), is the smallest unit of time used for sequencing note and automation events, both by step sequencers and in the MIDI standard.

If the resolution is too low (too few PPQN), the performance recorded into the sequencer may sound artificial (being quantised by the pulse rate), losing all the subtle variations in timing that give the music a "human" feeling. Purposefully quantised music can have resolutions as low as 24 (the standard for Sync24 and MIDI, which allows triplets, and swinging by counting alternate numbers of clock ticks) or even 4 PPQN (which has only one clock pulse per 16th note). At the other end of the spectrum, modern computer-based MIDI sequencers designed to capture more nuance are usually hardwired to 960 PPQN.

This resolution is a measure of time relative to tempo since the tempo defines the length of a quarter note and so the duration of each pulse.