When we did auditorium library music tests where a group of people all heard the same songs at the same time, we used 8 second hooks. That was proven to do two things: it gave time to identify the song and time to register on a dial or a paper form the score. Those tests could do up to about 600 songs in a session before fatigue set in.
Depending on the market, an incentive of between $60 and $150 would be given; the amount depended on the format and the economy of the market. Albuquerque got the lower amount and Long Island or Boston got the highest.
Recruiting does not identify the station. It is "blind" and people are invited, by phone in the past and by phone or email now, if they meet certain criteria such as age, gender, ethnicity and total use of radio. Then, often, they are played 3 to 5 sets of 3 hooks of songs that are within the scope of the station's target. For example, for a classic hits station, one set of three might include a borderline rock tune and two mainstream ones. Another would have a very light ballad that was very AC. And another would represent the core of the station. To be invited to the test, the candidate had to like at least two of the three (or 3 of the five).
For in-person tests in the past, a local recruiter was used... the same kind of recruiting recruiter gets samples for consumer research on cars and laundry detergents, too.
Callout for currents used about 25 to 30 hooks of the same length and the listener scored with the buttons on their phone. The same hook length was employed. Fatigue set in at about 35 songs, so most of us who did research stayed on the safe side, particularly if there were 18-24's in the sample.
Now we do the tests online, although the recruiting is still done personally and with the same specific targets. People are recruited to participate and some kind money or gift card reward is given.
The current song research uses up to 35 or 40 songs in a session. The recurrent / gold research does as many as 600 songs, but in several sessions, perhaps over a week's time; each research company has their own strategy or "feel" for library testing.
The interesting thing is that as soon as a listener scores a song, they get another hook to judge. The hoods can be as long as one wants, but 90% are scored in 6 seconds or less and 95% are scored in 8 seconds. When research is done on the few cases where over 8 seconds is taken, we find that recruits say, "I love that song and I just wanted to hear more of it".
Nobody needs more than 8 seconds to accurately say whether they know the song, used to like it and are burnt out on it or pick a number on a scale to show how much they like it. Each research company has its own scale. I like a "slider" that is labeled from "I hate it" to "I dislike it" to "neither like nor dislike" to "I like it" and "I love it".
I've done well over 1000 music tests with about 100,000 total persons back in the day when we did them in person at meeting rooms, wedding reception centers, church assembly rooms and even school auditoriums and community centers. Many of those I actually moderated as I was training staff. I've spoken with hundreds of people after the test and at breaks when they wanted to ask questions or make comments.
And that is just for music tests. Callout is bit different, and so are one-one-one or focus group perceptuals as well as "big book" format searches and studies about a whole station and competitors.
That's because national media, even going back to music shows by the Big Bands and crooners in the 30's and 40's were done on networks... radio back then and TV now. The big hits in every format have been national going back to the days of sheet music over 100 years ago.
The mistake here is saying "pick". The radio groups don't "pick" the songs. The listeners do. And generally, they like the same songs. Local differences are influenced by the competition, burn on individual songs due to excessive play in the market and other local differences in competitors, the station´s target ages and the like.
And when we do research, we don't play favorites. We just want to see how much listeners in a very specific target group want to hear songs on the radio today.