An OSC bundle groups multiple messages with a shared timetag so they are dispatched atomically at the same time

An OSC bundle begins with the marker #bundle followed by a timetag (an NTP timestamp) and a sequence of size-prefixed elements, each of which may be a message or a nested bundle. When the receiver’s time matches the timetag, all messages in the bundle are dispatched simultaneously. The special timetag value of 1 (64-bit, all zeros except the lowest bit) means ‘immediately.’ AbletonOSC’s client.py send_bundle() wraps a list of (address, params) pairs into a bundle with a current-time timetag, so a set of Live parameters change atomically in the same processing cycle rather than arriving as separate UDP datagrams that could be handled across different ticks.

Examples

Python: bundle_builder = OscBundleBuilder(IMMEDIATELY); add each OscMessage; bundle = bundle_builder.build(); client.send(bundle). AbletonOSC client.py: client.send_bundle([(‘/live/track/set/volume’, (0, 0.8)), (‘/live/track/set/mute’, (1, 0))]).

Assessment

Why would you use an OSC bundle rather than two separate OSC messages to simultaneously set two track volumes? What is the special timetag value meaning ‘dispatch immediately’?