IUP Portable User Interface might be a bit more popular than PortAudio. We know about 1 link to it since March 2021 and only 1 link to PortAudio. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
FYI PyAudio built on this software: http://portaudio.com/ which interfaces directly with Alsa/OSS (refer to the sounds system page, I'm not saying Open-Source Software here) which PulseAudio also does. Source: about 3 years ago
As C libraries, I can recommend IUP. You can also choose immediate mode which has the same look on all platforms, there are some wrappers around imgui in Zig like zig-upaya. Source: almost 3 years ago
JUCE - JUCE is a wide-ranging C++ class library for building rich cross-platform applications and plugins...
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RtAudio - RtAudio is a set of C++ classes that provide a common API for realtime audio input/output across...
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OpenAL Soft - OpenAL Soft is an LGPL-licensed, cross-platform, software implementation of the OpenAL 3D audio API.
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.