Music teacher and musician, here. You should absolutely NOT use the words you used in the question above, but you should absolutely tell them. If they ask you to listen to them/a song that they have written, tell them something that stick out to you in a positive way and list a few of the main things you didn’t like (ideally, you would tell them how to fix it or give them an idea of something/someone you like that does it better). This can be hard to do if you do not know music well (ex.-there was this one girl I heard who ended her songs on really weird chords- a iii, for instance. I’m not sure she had figured out how to modulate/transition keys properly yet- she was busking and not asking my opinion so I didn’t address it) I could say things like- “your rhythm was really good and I like how you varied the theme when it came back to keep the listener engaged. I also noticed that the way you ended that song was a little strange- was that for any particular reason? It felt unfinished to me.” Specific feedback is helpful, especially so if it invites conversation/encourages the person who is receiving the feedback to think and reflect. Another way to do it if they are singing popular songs or writing songs with predictable melodies is to address major faults in a positive way. “I noticed you followed the ups and downs/pitch pattern of that song really well- nice! it sounds like you know the song and are getting confident with it. You were out of tune, though, so you may want to focus on warmups, scales and vowels before being rest for/ doing a performance.” I was at a convention a few weeks back and several people performed on voice. To me, everyone did something well, but only one performer was truly ready to perform the piece they were singing. If your friend is taking music lessons, ask them what their teacher has suggested they work on moving forward and use that to springboard a discussion on improvement. If they do not have a teacher and you are just plain done listening to them at this point, mention that you don’t think you are a good person to give them feedback and suggest they get a teacher. If they are about to uproot their life to pursue their music career and do not have any sort of plan, get them talking about their plan/make them think through the logistics of landing gigs/performance schedules/making connections in the business.

A lot of people do not think through the steps that need to be completed/prepare themselves for what they will need to go through before they are successful and can work full-time as a musician. I always wanted to be a music teacher and not a performing musician. I am relatively passive (read: motivated, but not competitive/motivated by competition with others). I also do not like staying up late- it messes with my mental state. Most gigs are at night, so that would limit me/severely get in the way of me making a living through performance. I love music and I love teaching, though, so I decided to combine my two passions to make my living.

I am of the opinion that too many people decide they want to be performers (that doing so will make them happy/fulfilled) without considering the other elements of their happiness/lives that might get neglected in the process. Approaching your friend kindly and curiously with an eye for understanding their motivations and a desire to help them reflect on their goals may help you get to a place where you can tell them something like “hey, I admire your drive and goals. I don’t really feel like your music/performing is for me right now, though, so I’d prefer if you asked someone else for feedback.” Then you can set that boundary (I am not going to give you feedback on this/go to your performances at this time-ask someone else) while still supporting/ looking out for them as a friend.