Then.

• <bgsound src="ghostbusters.mid" autostart="true" loop="999"> (IE)
• <embed src="sound.wav" volume="50" controls="console">
• <object type="audio/x-wav" data="test.wav"></object> (IE)
• navigator.plugins['LiveAudio']['audio/wav'] (Netscape)
• Flash-based player UI, SWF object/embed
• Java Applets, Quicktime etc.

• 

  archive.org/details/WebRadio99

Now.

• 100% Flash-based audio (SWF object/embed)
• HTML5 Audio() / <audio>, with Flash fallback

HTML5 Audio specifics: Gotchas

• iOS: Only one sound at a time. No auto-play allowed (pop-up blocker-style security model.) Limited or no caching.
• No HTML5 audio/video support in Safari/Windows if QuickTime is not installed.
• No panning (not in spec?)
• Latency between JS/browser, and browser/hardware (per-browser, per-OS?)
• Browsers may vary on Audio() object ceiling (eg., 32 max?)
• HTTP: Partials (range requests) and chunked transfers de-emphasize "load progress"
• Related: areweplayingyet.org (HTML5 audio test suite)

HTML5 Audio specifics: Bugs

• new Audio().canPlayType('audio/mp3'): Mixed format support between MP3, MP4, OGG, WAV
• Broken HTML5 audio (intermittent play failure) on Safari, OS X Snow Leopard (OS X 10.6.3 - 10.6.7.)
• new Audio(null) (may load "null" in Webkit) vs. new Audio() (WRONG_ARGUMENTS_ERR in Opera 9.64) - related: audio.src = null vs. audio.src = '' (Firefox likes '', most others don't and fail to close open connection, may not free RAM etc.)

Using HTML5 Audio today

• JavaScript + Flash: Hybrid API approach

  soundManager.createSound({
    id: 'mySound',
    url: '/path/to/an.mp3'
  }).play();

• SoundManager 2: JavaScript API for MP3, MP4 + HTML5 audio. Hidden Flash abstraction. 10 KB (gzip)

Practical examples

• schillmania.com/projects/soundmanager2/
• jplayer.org (jQuery-based player UI)

Less-practical examples

• YUI + SoundManager 2: A Noisy DOM
• wheelsofsteel.net (browser-based DJ turntable + mixer experiment; HTML5 and/or Flash)

Future?

• HTML5 audio support is improving; quirks remain to be found + worked out.
• MP3 + MP4 vs. "free" (OGG/WebM) format wars, fragmented format support may be the norm
• Mozilla Audio Data API and Webkit Web Audio APIs (create and manipulate audio data on the fly, from JS.) Low-level control, relative to Audio().