Section 29 of 30 · about 4 min read · updated October 2026

29Open questions and known gaps

What we could not pin down, so you know where the edges of this guide are:

Exact "firsts". The SL-P1200's 1986 date, Final Scratch's release year, the Denon DN-2000F's year (1991-92 versus 1993), the DJM-500's year (1994 versus 1995), the first full-color LED video display and the first laser-phosphor moving head all lack a neutral primary source.
The Wall of Sound's numbers. Driver counts run from about 586 to 650, the published wattage does not match the published amplifier count, and "first line array" rests on a 2001 article we could not read.
Crowd and attendance figures. Jarre's records are self-reported or Guinness figures nobody has independently checked; festival numbers are promoter-reported and count attendance across days.
Incident tolls. Pukkelpop 2011 is commonly given as five dead, unverified from an official source; Indiana 2011 injuries are given as "more than 40" or 58; the Moscow 2008 laser injuries as 29 or 35. Tolls for recent fires moved after first reports (Kočani from 59 to 63, Crans-Montana from 40 to 41) and may move again.
Tomorrowland 2025. The cause of the mainstage fire is unconfirmed, the destroyed stage's size is given as 45 by 160 meters or 50-plus by 140, and the replacement's build time as under 24, 36 or under 48 hours.
The Event Safety Alliance's founding. Formed in early 2012 by its own account, but it marks its anniversary from 2011, the year of the collapse that prompted it.
Corporate deals. inMusic is integrating Native Instruments, but we found no formal closing announcement; nor any statement that the CDJ-3000 is discontinued, as of October 2026.
Standards and platform terms. Our 2026-edition details for NFPA 1126 and 160 come from a publisher's summary, not the standards themselves; Twitch DJ Program terms are as announced in 2024; Sphere's residency list comes from Wikipedia rather than Sphere.
CDJ-3000 and 3000X interoperability on the same PRO DJ LINK network: no primary source.
Audience-scanning exposure limits. We deliberately give no single number, because the real limit depends on wavelength and exposure time and the standards that define it were not available to us.
Variance details. What a US variance holder may and may not do - operate under someone else's variance, rent to non-holders - is set in individual approval letters we have not seen.
Booth and riser design. No citable source for booth heights, bass isolation or deck stability.
Rigging specifics. ESTA's hoist and truss standards, typical arena point loads, and who formally signs off a rigging plot.
Costs. No reputable public figures for crew day rates, per diems or trucking; the numbers we have are rock-act anecdotes.
Sound limits. The European table is a 2019 snapshot; national rules may have moved since.
US electrical code. Section numbers come from secondary sources, and jurisdictions adopt different editions of the NEC.
Settlement mechanics and the technical-versus-hospitality rider split are trade knowledge without a published standard.
Scene firsts and dates. The first house record, who named jungle, the origin of new beat, Shoom's opening date, when Frankie Knuckles left the Warehouse (late 1982 or 1983), and the Paradise Garage's closing date (26 September or 1 October 1987) all have competing accounts.
Scenes we could not cover properly. Colombia's picó sound systems, Brazilian and Colombian club and festival scenes, Japan's club history, Australia, Israel's psytrance scene and kwaito's 1990s origins were not researched to the standard of the rest of this guide.
Form 696. Its scrapping in 2017 is widely reported, but we did not verify it.
The Live Nation-Insomniac deal. Usually described as a 50% stake for about $50 million; the official terms were never disclosed.
DJ fees. No primary source for any per-show superstar fee or Las Vegas residency deal; Forbes' DJ earnings list appears to have stopped after 2019, which we could not confirm.
Deal terms. No survey of how often DJ deals are flat, versus or door deals, no source defining a "buyout", and the 50% deposit norm rests on one attorney's account. No 2025-26 data on whether production costs have fallen back.
The ticket split. NITO's breakdown is an advocacy estimate built on band touring, and its own coverage gives two different fee shares (over 20% and 28%).
Strobe rules. We could not locate the HSE document behind the four-flashes-a-second club recommendation, could not read Ofcom's guidance directly, and found no legal requirement for strobe warning signs.
Access data. The best UK figures on viewing platforms date from 2011-13; there is no data on how many festivals provide sign language interpreting, and no reputable source on sensory maps, calm spaces or welfare-team staffing.
US naloxone and free water. Naloxone's US status has changed since the 2022 reporting we rely on, and we found no US statewide free-water requirement. A claim that the US Department of Justice clarified in 2017 that free water and drug education do not violate the RAVE Act appears in some coverage, but we could not find a primary source, so this guide does not repeat it.
Drone records. The Liuyang count (15,947 or 15,974) is unconfirmed against Guinness, and the cause of the canceled Vietnam shows is unknown.
Spatial audio and "AI". Sphere's audio claims have no published measurements; we found no source for d&b Soundscape in clubs, or for how Anyma's Sphere visuals were made.
Timecode. No source documents a fully timecode-locked electronic dance music festival show across every department, or a defined "playback engineer" role in electronic touring.
Green claims. No independent audit of Tomorrowland, DGTL or Boom's figures; the full A Greener Festival 2023 method and sample were not available to us; no Clean Scene follow-up since 2021.
Crew mental health. The "five to 10 higher" figure for touring professionals is ambiguous between percentage points and multiples.
Images. Several illustrations a guide like this should have - a Technics SL-1200, a gobo, a line array, a CO2 jet, the Wall of Sound, the Mothership - could not be found under an open license we could verify.

If you know the answer to any of these, and can point to where it is written down, that is exactly the kind of correction this guide exists to take.