librtmidi4 binary package in Ubuntu Focal arm64

 RtMidi is a set of C++ classes that provides a common API (Application
 Programming Interface) for realtime MIDI input/output across Linux
 (native ALSA, JACK, and OSS), Macintosh OS X, SGI, and Windows
 (DirectSound and ASIO) operating systems. RtMidi significantly
 simplifies the process of interacting with computer audio hardware. It
 was designed with the following objectives:
 .
  * object-oriented C++ design
  * simple, common API across all supported platforms
  * only one source and two header files for easy inclusion in
    programming projects
  * MIDI device enumeration
 .
 MIDI input and output functionality are separated into two classes,
 RtMidiIn and RtMidiOut. Each class instance supports only a single MIDI
 connection. RtMidi does not provide timing functionality (i.e., output
 messages are sent immediately). Input messages are timestamped with delta
 times in seconds (via a double floating point type). MIDI data is passed
 to the user as raw bytes using an std::vector<unsigned char>.
 .
 This package provides the shared library.

Source package